tag:theconversation.com,2011:/us/topics/seismic-activity-53444/articlesSeismic activity – The Conversation2023-02-08T17:28:30Ztag:theconversation.com,2011:article/1995402023-02-08T17:28:30Z2023-02-08T17:28:30ZTurkey-Syria earthquakes: shallow depth of main shocks is a key reason why they’ve been so devastating<p>The <a href="https://bbcgossip.com/news/timeline-turkey-hit-by-most-devastating-earthquake-since-1999/">earthquakes that struck in Turkey and Syria</a> in the early hours of February 6 have led to terrible destruction on a scale not seen in Europe for many decades. At the time of writing, the <a href="https://www.theguardian.com/world/live/2023/feb/08/turkey-syria-earthquake-death-toll-homeless-disaster-latest-updates">death toll</a> has risen beyond 11,000 people and will continue to rise over the coming days and weeks. Hundreds of thousands more have lost their homes.</p>
<p>There are many reasons why the death and devastation have been so terrible. First and foremost, the sheer magnitude of the two main events and their associated aftershocks. These earthquakes, which measured <a href="https://theconversation.com/turkey-syria-earthquakes-a-seismologist-explains-what-has-happened-199340">7.8 and 7.5</a> on the <a href="https://www.usgs.gov/faqs/moment-magnitude-richter-scale-what-are-different-magnitude-scales-and-why-are-there-so-many">moment magnitude scale</a>, each released roughly as much energy as the largest-ever atomic bomb test carried out during the Cold War – <a href="https://www.nationalww2museum.org/war/articles/tsar-bomba-largest-atomic-test-world-history">around 50 megatons</a>, in 1961 by the former Soviet Union. And there were two of these events in the same region, separated by a matter of hours. </p>
<p>To this we have to add the clusters of <a href="https://www.dw.com/en/earthquake-in-turkey-whats-going-on-with-the-aftershocks/a-64632843">aftershocks</a> which follow on from the main events. These are smaller (mostly lower than magnitude 5) but will continue for several days, gradually decreasing in intensity and regularity. They are nevertheless dangerous, as buildings already seriously weakened by earlier events may be caused to collapse. This inevitably further hampers rescue attempts in the region.</p>
<p>Another factor is the timing of the first and largest earthquake. It occurred at 4.17am local time, when most people would have been asleep in their homes. During an earthquake, the great majority of casualties are caused not by the shaking, but by the resulting collapse of buildings. The timing of this event was about as bad as it possibly could be – many people had very little opportunity to escape from their homes in time. This is likely a major factor in the very high number of deaths and injuries.</p>
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<h2>Depth charge</h2>
<p>But a key geological contribution to the devastation was the relatively <a href="https://www.usgs.gov/programs/earthquake-hazards/determining-depth-earthquake">shallow depth</a> of the earthquake hypocentres: 18km for the first 7.8 event and 10km for the later 7.5 shock.</p>
<p>The <a href="https://www.euston96.com/en/hypocenter/#:%7E:text=The%20hypocenter%20of%20an%20earthquake%20is%20the%20place,seismic%20waves%20that%20are%20directed%20in%20all%20directions.">hypocentre</a> is the point at which the fault begins to rupture at depth. In global terms, these are relatively near-surface shocks. There are two reasons why this leads to a greater degree of destruction.</p>
<p>Put simply, the first reason is that the shallower an earthquake is, the closer the Earth’s surface is to the hypocentre. This means that the ground shaking is more intense and destructive. There is less opportunity for the shockwaves to dissipate, as happens when earthquakes occur deeper in the Earth and they travel through tens of kilometres of rock.</p>
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<p>The second reason is that the faults that generate earthquakes larger than 5.5 are more likely to rupture through to the surface. This creates – almost instantaneously – a <a href="https://www.seismicresilience.org.nz/topics/seismic-science-and-site-influences/earthquake-hazards/ground-shaking-2/#:%7E:text=Ground%20displacement%20is%20how%20far,other%20areas%20of%20land%20nearby.">ground displacement</a> whereby one part of the ground literally moves by several metres relative to an adjacent part. </p>
<p>These surface breaks – also known as “<a href="https://www.usgs.gov/faqs/what-relationship-between-faults-and-earthquakes-what-happens-fault-when-earthquake-occurs">capable faults</a>” – are incredibly damaging. They can lead to the severing of major subsurface and surface infrastructure including water mains, electricity cables, gas pipelines and tunnels. </p>
<p>There are already <a href="https://www.offshore-technology.com/news/turkey-earthquake-damages-gas-pipeline/">reports of damage to pipelines</a> in Turkey following the February 6 events. Spectacular satellite images and ground-based photographs are also emerging of offset roads and railway lines, as well as serious damage to buildings that straddle the ruptures. All of this occurs in addition to the damage caused by shaking, <a href="https://en.wikipedia.org/wiki/Soil_liquefaction">liquefaction</a> of soft sediment in valleys, and landslides.</p>
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<img alt="Three-metre rupture in a road caused by the 2023 Turkish eathquake." src="https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508978/original/file-20230208-31-92pnwj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A three-metre rupture in the Kahramanmaraş-Gaziantep highway, close to the village of Tevekkelli in the earthquake zone.</span>
<span class="attribution"><span class="source">Hasan Sözbilir/Eskişehir Osmangazi University</span>, <span class="license">Author provided</span></span>
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<p>In a <a href="https://www.veryansintv.com/prof-dr-sozbilir-en-az-3-fay-segmenti-kirilmis-oldu/">recent blog</a>, Professor Hasan Sözbilir of the Dokuz Eylül University Earthquake Application and Research Centre has studied the region and reported: “As far as I can see, at least three fault segments have been broken. The total length of the surface fracture has exceeded 500km.”</p>
<p>So why were these events relatively shallow in this region? Some of the largest earthquakes known to have occurred are associated with the so-called “<a href="https://education.nationalgeographic.org/resource/ring-fire">Pacific Ring of Fire</a>”. These earthquakes are commonly generated as deep as 700km, as the strong, dense oceanic plates plunge down into the Earth below the surrounding continents. </p>
<p>Turkey, however, lies in a region of weaker, mainly continental <a href="https://education.nationalgeographic.org/resource/lithosphere">lithosphere</a> where the crust is only about 30 km thick, close to a point where three tectonic plates come together – Africa, Arabia and Anatolia. The convergence of the Arabian plate is squeezing the wedge-like Anatolian plate out to the west, generating a series of sub-vertical, <a href="https://www.usgs.gov/faqs/what-fault-and-what-are-different-types#:%7E:text=strike%2Dslip%20fault%20%2D%20a%20fault,of%20a%20right%20lateral%20fault.">strike-slip faults</a> such as the East Anatolian Fault, which failed during the magnitude 7.8 event.</p>
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<img alt="Map showing action of tectonic plates in vicinity of Turkey/Syria earthquake" src="https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=561&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=561&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=561&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=704&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=704&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508974/original/file-20230208-15-y1zna3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=704&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The movement of three competing tectonic plates causes frequent seismic activity in this region.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-021-86063-y">Meng, J., Sinoplu, O., Zhou, Z. et al. Greece and Turkey Shaken by African tectonic retreat. Sci Rep 11, 6486 (2021). https://doi.org/10.1038/s41598-021-86063-y</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
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<p>In such continental crust, the strongest part – and the most likely point for large earthquakes to be born – lies typically at between 10km and 20km depth. In settings of this kind, shallow, surface-rupturing faults are more likely to form.</p>
<h2>Wrong time, wrong place</h2>
<p>A third factor is simply that the region where the earthquakes occurred is highly populated. Given the timing, a substantial loss of life is almost inevitable following an event – or events – of this magnitude. </p>
<p>Deadly earthquakes are well known in Turkey. In the past 50 years, there have been at least <a href="https://www.ibtimes.sg/turkey-earthquake-2023-timeline-biggest-tremors-hit-country-recent-decades-68925">four major events</a> with substantial loss of life – in 1975, 1983, 1999 and 2020. Following the Izmit earthquake in 1999, there were serious efforts by the Turkish authorities to improve building standards to better resist earthquakes. </p>
<p>But there are limits as to what you can do in a highly populated area with events of this size. And we have to remember that the two main seismic shocks were perhaps more than twice as big as the largest known historical earthquake in this region.</p>
<p>Furthermore, in Syria we have to add the fact that years of <a href="https://theconversation.com/turkey-syria-earthquake-how-disaster-diplomacy-can-bring-warring-countries-together-to-save-lives-199329">ongoing civil conflict</a> have substantially degraded the building infrastructure, making the region event less resilient to the effects of seismic shaking. This will likely also hamper efforts to deliver assistance and aid – and, in the longer term, to rebuild.</p>
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Read more:
<a href="https://theconversation.com/turkey-syria-earthquake-how-disaster-diplomacy-can-bring-warring-countries-together-to-save-lives-199329">Turkey-Syria earthquake: how disaster diplomacy can bring warring countries together to save lives</a>
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<p class="fine-print"><em><span>Bob Holdsworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An earthquake expert explains why the death and devastation have been so terrible in Turkey and SyriaBob Holdsworth, Professor of Structural Geology, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1993892023-02-07T02:02:15Z2023-02-07T02:02:15ZEarthquake footage shows Turkey’s buildings collapsing like pancakes. An expert explains why<figure><img src="https://images.theconversation.com/files/508530/original/file-20230207-21-fclmjh.jpg?ixlib=rb-1.1.0&rect=40%2C0%2C4479%2C2983&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Mustafa Karali / AP</span></span></figcaption></figure><p>A pair of huge earthquakes have struck in Turkey, leaving <a href="https://www.bbc.com/news/world-europe-64533851">more than 3,000 people dead</a> and unknown numbers injured or displaced. </p>
<p>The first quake, near Gaziantep close to the Syrian border, <a href="https://earthquake.usgs.gov/earthquakes/eventpage/us6000jllz/executive">measured 7.8 in magnitude</a> and was felt as far away as the UK. The second occurred nine hours later, on what appears to be an intersecting fault, registering <a href="https://earthquake.usgs.gov/earthquakes/eventpage/us6000jlqa/executive">a magnitude of 7.5</a>. </p>
<p>Adding to the devastation, <a href="https://www.nytimes.com/2023/02/05/world/europe/turkey-earthquake-rescue.html">some 3,450 buildings have collapsed</a>, according to the Turkish government. Many of the modern buildings have failed in a “<a href="https://www.newcivilengineer.com/archive/pancake-collapses-tell-story-of-poor-construction-15-02-2001/">pancake mode</a>” of structural collapse. </p>
<p>Why did this happen? Was it simply the enormous magnitude and violence of the quake, or is the problem with the buildings?</p>
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Read more:
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<h2>Thousands of years of earthquakes</h2>
<p>Earthquakes are common in Turkey, which sits in a very seismically active region where three tectonic plates constantly grind against one another beneath Earth’s surface. Historical records of earthquakes in the region go back at least 2,000 years, to <a href="https://en.wikipedia.org/wiki/AD_17_Lydia_earthquake">a quake in 17 CE</a> that levelled a dozen towns. </p>
<p>The East Anatolian Fault zone that hosted these earthquakes is at the boundary between the Arabian and Anatolian tectonic plates, which move past each other at approximately 6 to 10 mm per year. The elastic strain that accumulates in this plate boundary zone is released by intermittent earthquakes, which have occurred for millions of years. The recent earthquakes are thus not a surprise.</p>
<p>Despite this well-known seismic hazard, the region contains a lot of vulnerable infrastructure.</p>
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Read more:
<a href="https://theconversation.com/earthquakes-dont-kill-our-collapsing-structures-do-so-how-can-we-build-them-to-stay-up-64443">Earthquakes don't kill, our collapsing structures do. So how can we build them to stay up?</a>
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<p>Over the past 2,000 years we have learnt a lot about <a href="https://asia.nikkei.com/Business/Business-Spotlight/How-Japan-s-builders-absorbed-the-lessons-of-the-2011-earthquake">how to construct buildings</a> that can withstand the shaking from even severe earthquakes. However, in reality, there are many factors that influence building construction practices in this region and others worldwide.</p>
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<h2>Poor construction is a known problem</h2>
<p>Many of the collapsed buildings appear to have been built from concrete without adequate seismic reinforcement. Seismic building codes in this region <a href="https://doi.org/10.1088/1757-899X/737/1/012015">suggest</a> these buildings should be able to sustain strong earthquakes (where the ground accelerates by 30% to 40% of the normal gravity) without incurring this type of complete failure. </p>
<p>The 7.8 and 7.5 earthquakes appear to have caused shaking in the range of 20 to 50% of gravity. A proportion of these buildings thus failed at shaking intensities lower than the “design code”. </p>
<p>There are <a href="https://revkin.substack.com/p/gauging-losses-and-lessons-in-turkeys">well-known problems in Turkey</a> and elsewhere with ensuring safe building construction and adherence to seismic building codes. Similar building collapses have been seen in <a href="https://www.washingtonpost.com/wp-srv/inatl/daily/aug99/buildings21.htm">past earthquakes in Turkey</a>.</p>
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<img alt="An aerial photo of a collapsed building." src="https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508541/original/file-20230207-17-hnmtis.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A known problem: a collapsed apartment building after the 1999 earthquake in Izmit, Turkey.</span>
<span class="attribution"><span class="source">Hurriyet / AP</span></span>
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<p>In 1999, a huge quake near Izmit saw some 17,000 people dead and as many as <a href="https://ilkha.com/english/analysis/today-marks-the-21st-anniversary-of-marmara-earthquake-9525">20,000 buildings</a> collapse.</p>
<p>After a quake in 2011 in which hundreds of people died, Turkey’s then prime minister, Recep Tayyip Erdogan, <a href="https://www.theguardian.com/world/2011/oct/26/turkey-earthquake-building-negligence-erdogan">blamed</a> shoddy construction for the high death toll, saying: “Municipalities, constructors and supervisors should now see that their negligence amounts to murder.”</p>
<h2>Reconstruction</h2>
<p>Even though Turkish authorities know many buildings are unsafe in earthquakes, it is still a difficult problem to solve. Many of the buildings are already built, and seismic retrofitting may be expensive or not considered a priority compared to other socio-economic challenges.</p>
<p>However, reconstruction after the quake may present an opportunity to rebuild more safely. In 2019, Turkey <a href="https://www.preventionweb.net/news/turkiye-building-resilience-against-earthquakes">adopted new regulations</a> to ensure buildings are better equipped to handle shaking. </p>
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<p>While the new rules are welcome, it remains to be seen whether they will lead to genuine improvements in building quality.</p>
<p>In addition to substantive loss of life and infrastructure damage, both earthquakes are likely to have caused a myriad of environmental effects, such as ruptured ground surfaces, liquified soil, and landslides. These effects may render many areas unsafe to rebuild on – so reconstruction efforts should also include <a href="https://nhess.copernicus.org/articles/20/3361/2020/">planning decisions about what can be built where</a>, to lower future risks.</p>
<p>For now, aftershocks continue to shake the region, and search and rescue efforts continue. Once the dust settles, reconstruction will begin – but will we see stronger buildings, able to withstand the next quake, or more of the same?</p>
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Read more:
<a href="https://theconversation.com/earthquake-in-turkey-and-syria-how-satellites-can-help-rescue-efforts-199357">Earthquake in Turkey and Syria: how satellites can help rescue efforts</a>
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<p class="fine-print"><em><span>Mark Quigley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When Monday’s earthquake struck, many poorly constructed buildings suffered a ‘pancake mode’ collapse.Mark Quigley, Associate Professor of Earthquake Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1951102022-11-23T00:14:34Z2022-11-23T00:14:34ZWhy are shallow earthquakes more destructive? The disaster in Java is a devastating example<figure><img src="https://images.theconversation.com/files/496690/original/file-20221122-21-ur5ids.jpg?ixlib=rb-1.1.0&rect=362%2C51%2C8083%2C5691&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A man reacts as he inspects the damage caused by Monday's earthquake in Cianjur, West Java, Indonesia.</span> <span class="attribution"><span class="source">Tatan Syuflana/AP</span></span></figcaption></figure><p>On November 21 2022 an earthquake near the Indonesian city of Cianjur in West Java caused at least <a href="https://www.bbc.com/news/world-asia-63712461">268 deaths and damaged 22,000 buildings</a>.</p>
<p>At magnitude 5.6, this earthquake was much smaller than many <a href="https://www.ngdc.noaa.gov/hazel/view/hazards/earthquake/search">other earthquakes</a> that have caused death and destruction in Indonesia over the past few decades. </p>
<p>Why is this one so different? One of the main reasons the Cianjur earthquake was so destructive was its shallow depth of 10km.</p>
<p>This event should serve as a wake-up call to improve building practices in Indonesia, because we know from the past that much larger shallow events can occur in Java; it’s not a question of if but when.</p>
<h2>The role of earthquake depth</h2>
<p>Two of the most important factors that determine the intensity of ground shaking caused by an earthquake are its magnitude and distance.</p>
<p>Large earthquakes of greater than 50km depth can and do cause widespread damage, but the intensity of shaking is reduced because the seismic waves travel at least 50km before they reach people.</p>
<p>Such earthquakes rarely cause massive fatalities – the magnitude 6.5 Tasikmalaya, Java earthquake in 2017 occurred at 90km depth and <a href="https://www.ngdc.noaa.gov/hazel/view/hazards/earthquake/event-data?maxYear=2017&minYear=2017&minDeaths=4">killed only four people and damaged 4,826 homes</a>. </p>
<p>The recent Cianjur earthquake was much smaller – at magnitude 5.6, its energy was 21 times smaller than the Tasikmalaya earthquake, but it did much greater damage.</p>
<p>The Cianjur earthquake had a greater impact because it ruptured within a few kilometres of the city of Cianjur, where the shaking was classified as “severe” (<a href="https://www.usgs.gov/programs/earthquake-hazards/modified-mercalli-intensity-scale">Modified Mercalli Intensity</a> 8). </p>
<p>A similar comparison could be made with giant subduction zone earthquakes that occur offshore. While these can be far greater in size than this week’s Java earthquake, they are generally 100km or more distant from population centres, so they kill fewer people through building collapse.</p>
<h2>Infrequent danger</h2>
<p>There is another reason inland shallow earthquakes can be so devastating, particularly in Java: they occur infrequently, so most people are oblivious to the danger. </p>
<p>The population of Java increased by <a href="http://www.bps.go.id/tab_sub/view.php?kat=1&tabel=1&daftar=1&id_subyek=12&notab=1">a factor of four</a> through <a href="https://www.researchgate.net/publication/235003003_Mortality_from_the_influenza_pandemic_of_1918-19_in_Indonesia/link/55ba347408ae9289a0926b9f/download">the 20th century</a>, and during this time there was only one shallow earthquake in 1924 that caused nearly 800 deaths, and another four that caused between 10 and 100 deaths.</p>
<p>It wasn’t until 2006 that a really major event occurred: the 2006 Yogyakarta earthquake, <a href="https://www.ngdc.noaa.gov/hazel/view/hazards/earthquake/event-data?maxYear=2022&maxLongitude=119.0394401550293&minYear=1900&maxLatitude=-5.482546633157073&minDeaths=10&minLongitude=104.7572135925293&minLatitude=-9.75017078272175">magnitude 6.3</a>, which killed killed 5,749 people. </p>
<p>Elsewhere in Java there is no lived experience of a major earthquake, often stretching back several generations.</p>
<p>As a consequence, little attention is paid to the earthquake resilience of residential construction, so when an earthquake does occur many of the weak buildings will collapse.</p>
<h2>A starkly different colonial past</h2>
<p>Java’s earthquake history during the colonial era paints a starkly different picture. Our <a href="https://pubs.geoscienceworld.org/ssa/bssa/article/doi/10.1785/0120220047/618736/Gempa-Nusantara-A-Database-of-7380-Macroseismic">recent study</a> shows many damaging earthquakes have occurred in Java since the 17th century. At least nine earthquakes since 1865 have caused shaking so severe they were almost certainly shallow events.</p>
<p>These include two earthquakes near Wonosobo in central Java in 1924 that caused catastrophic mudslides that killed nearly 900 people.</p>
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<a href="https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sepia photo showing a small, entirely collapsed building" src="https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/496722/original/file-20221122-16-xu4jmg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Earthquake damage in Cianjur, Jawa Barat, in March 1879.</span>
<span class="attribution"><a class="source" href="https://digitalcollections.universiteitleiden.nl/view/item/826282">Leiden University Libraries Digital Collections</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>In our <a href="https://pubs.geoscienceworld.org/ssa/bssa/article/doi/10.1785/0120220047/618736/Gempa-Nusantara-A-Database-of-7380-Macroseismic">recent study</a> we also documented extremely violent shaking caused by the October 25 1875 earthquake near Kunningan in West Java. An eyewitness described being thrown off a chair and saw a herd of cows being knocked off their feet.</p>
<p>Cirebon also experienced a damaging earthquake on November 16 1847 which is thought to have caused a <a href="https://iopscience.iop.org/article/10.1088/1755-1315/873/1/012052/meta">river channel offset of 5 metres</a>, suggesting a magnitude of 7 or greater. </p>
<p>Cianjur, the site of this week’s earthquake, has experienced at least one damaging earthquake, on March 28 1879, which caused the collapse of several buildings in Cianjur with some loss of life. </p>
<h2>A fact of life</h2>
<p>Geologists understand well that earthquakes are a fact of life in Java. In work over the past two decades they have <a href="https://pubs.geoscienceworld.org/earthquake-spectra/article-abstract/36/1_suppl/112/592080/Development-of-the-2017-national-seismic-hazard?redirectedFrom=fulltext">identified many faults</a> – cracks or joints in Earth’s crust – in Java that are likely to be active, but only a handful of these have been studied in detail.</p>
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<strong>
Read more:
<a href="https://theconversation.com/why-do-people-in-indonesia-still-live-in-disaster-prone-areas-105868">Why do people in Indonesia still live in disaster-prone areas?</a>
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<p>The Lembang Fault on the outskirts of Bandung, Indonesia’s fourth-largest city (population 8.8 million, as opposed to Cianjur’s 170,000), is one of the few for which <a href="https://www.sciencedirect.com/science/article/pii/S0040195118304268">geologic evidence</a> of prehistoric earthquake activity has been established. This fault is thought to be capable of producing a magnitude 6.5–7.0 earthquake every 170–670 years.</p>
<p>Other active faults are known to threaten the cities of Jakarta, Surabaya and Semarang, in addition to Yogyakarta. And these are just the ones we know about.</p>
<h2>Preparing for the next quake</h2>
<p>Shallow earthquakes could occur that are much larger than the Cianjur earthquake, next to cities that are much larger than Cianjur. What can Indonesia do to avoid massive fatalities in such an event?</p>
<p>The typical answer is to improve – and enforce – building codes, forcing any new construction to be more earthquake-resilient.</p>
<p>Indonesia does have a building code based on a modern seismic hazard map, but it is only applied to buildings of eight floors or higher. Given the high poverty level in Indonesia, universal enforcement of the building code is regarded as impractical. </p>
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<strong>
Read more:
<a href="https://theconversation.com/we-may-never-be-able-to-predict-earthquakes-but-we-can-already-know-enough-to-be-prepared-168480">We may never be able to predict earthquakes – but we can already know enough to be prepared</a>
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<p>An alternative may be the adoption of simple, minimum standards for concrete strength, quality of reinforcement and other aspects of building practice that may not conform to the building code, but at least afford a higher level of protection than current practice.</p>
<p>Any change in building practice requires a change in culture: people have to expect more of builders, and be willing to pay for it.</p>
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<p><em>Correction: This article has been updated to correct two points – the recent Cianjur earthquake was 21 times smaller than the Tasikmalaya earthquake, not eight times smaller. Additionally, it was clarified that the 1847 earthquake caused a river channel offset.</em></p><img src="https://counter.theconversation.com/content/195110/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stacey Servito Martin is supported by a research scholarship from the Australian National University. </span></em></p><p class="fine-print"><em><span>Mudrik Rahmawan Daryono and Phil R. Cummins do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Java quake was so devastating in part because it occurred so close to the surface.Phil R. Cummins, Professor, Australian National UniversityMudrik Rahmawan Daryono, Senior research scientist, Badan Riset dan Inovasi Nasional (BRIN)Stacey Servito Martin, PhD Candidate, Earth Sciences, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1857082022-07-03T19:53:36Z2022-07-03T19:53:36ZNot if, but when: unless Papua New Guinea prepares now, the next big earthquake could wreak havoc in Lae<figure><img src="https://images.theconversation.com/files/471776/original/file-20220630-11-7veu8b.jpeg?ixlib=rb-1.1.0&rect=106%2C98%2C5836%2C3858&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Brendan Esposito/AAP</span></span></figcaption></figure><p>Earthquakes can be especially devastating for developing countries, where competing priorities can stymie resource allocation towards earthquake resilience.</p>
<p>Even in tectonically active areas, where tectonic plates meet and scrape against one another, large earthquakes may not occur often enough to seem like a priority compared to more immediate concerns. That is, until one devastates a populated area, as we’re now seeing with the tragedy <a href="https://www.theguardian.com/world/2022/jun/25/taliban-say-they-will-not-interfere-with-afghanistan-earthquake-aid">in Afghanistan</a>. </p>
<p>Nowhere is this more true than in Papua New Guinea. PNG is situated in one of the most tectonically active areas in the world – one that <a href="https://link.springer.com/article/10.1007/s10518-020-00966-1">experiences</a> more than 100 earthquakes of magnitude five or greater each year.</p>
<p>PNG’s stability and economic development are of great interest to Australia. Yet earthquake scientists know recent development gains could be threatened by earthquakes. </p>
<p>We helped create an updated national seismic hazard map for PNG based on modern earthquake data and knowledge of active faults.</p>
<p>The map was developed in a partnership between Geoscience Australia and the PNG government’s Port Moresby Geophysical Observatory. First published <a href="https://link.springer.com/article/10.1007/s10518-020-00966-1">in 2019</a>, it’s now providing the backbone for our ongoing work into earthquake risk assessment and management in PNG. </p>
<h2>Eyes on Lae</h2>
<p>The high level of earthquake activity in PNG was already recognised in national earthquake hazard maps developed in <a href="https://bulletin.nzsee.org.nz/index.php/bnzsee/article/view/952/927">1982</a>. But the poor-quality data used in these early hazard maps resulted in broad areas of moderately elevated hazard – and did not reflect the very high hazard levels near active faults.</p>
<p>Worryingly, PNG’s current building codes are still based on these outdated maps. Buildings and infrastructure near active faults may be vulnerable to large, local earthquakes – particularly since PNG has adopted “Western” construction materials such as masonry, which can be less resilient than traditional wooden structures.</p>
<p>The latest national seismic hazard map shows a particularly pronounced hazard in Lae, PNG’s second-largest city. Lae sits adjacent to a major active tectonic plate boundary known as the Ramu-Markham fault system.</p>
<p>With a population of more than 100,000, many lives and livelihoods would be threatened by a large earthquake. Lae is also a major economic hub for the country. It has the largest port and is the starting point of the transport artery running through mainland PNG. </p>
<p>Concerns raised by the latest hazard map about Lae’s potential vulnerabilities has led us to initiate the Lae Earthquake Risk Project, involving the University of Technology in Lae and the University of Papua New Guinea in Port Moresby. </p>
<p>Our research goal is to better understand and model what the potential impacts of a Ramu-Markham earthquake may be, and how Lae can boost its resilience in the event of a major earthquake.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471528/original/file-20220629-18-wj7b12.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">We helped install a seismic sensor in New Britain, Papua New Guinea, in 2019. Similar seismic sensors will be installed in Lae as part of the new project.</span>
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<h2>How could a Ramu-Markham earthquake happen?</h2>
<p>Large earthquakes happen when two tectonic plates move against each other. </p>
<p>In the case of the Ramu-Markham fault system, two plates are converging, or moving towards each other. This movement results in friction along the fault, which builds up stress. An earthquake happens when the built-up stress surpasses the frictional strength along the fault. </p>
<p>While we often think of a geologic fault as a “line”, a major fault system like the Ramu-Markham consists of many segments. Any one of these segments (or a combination) may be active. </p>
<p>Segments are often overlapping, and each has a distinct level of activity. We can record this activity using precise GPS measurements of ground movements, also called “strain”. </p>
<p>Our work started by identifying exactly which segments of the Ramu-Markham fault system are active and accumulating strain energy that might be released in an earthquake. We found the ground movement in this fault system can be explained by activity on a single segment called the Gain fault. </p>
<p>This fault segment is more than 100km long and most of Lae lies within 15km of it. A large earthquake at this distance could cause widespread damage.</p>
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<img alt="Gain and Bumbu faults highlighted over a Google Maps screenshot of PNG" src="https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/471685/original/file-20220629-12-7oc2sa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The Gain and Bumbu faults are two parallel segments of the Ramu-Markham fault system that pass close to Lae.</span>
<span class="attribution"><span class="source">Author provided/Google Maps</span></span>
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<h2>The Bumbu fault</h2>
<p>Although GPS measurements of ground movement are consistent with activity being confined to the Gain fault only, this may not be the only way to explain the data. </p>
<p>The Bumbu fault is another segment of the Ramu-Markham fault system, further south, that cuts through Lae’s CBD. If it’s active, it is of potentially greater concern than the Gain fault.</p>
<p><a href="http://star.gsd.spc.int/star_abstracts/2001_MR0445.pdf">Studies</a> from the 1990s on the geology of Lae’s urban centre suggest a “major tectonic event” happened about 250 years ago, possibly on the Bumbu fault, which changed the course of the Bumbu River flowing through Lae today.</p>
<p>Although this event was prior to European contact, it’s supported by local oral histories and other analyses of elevation data taken from around Lae. Questions remain over whether it was a single major event, or a series of smaller events over an extended period.</p>
<p>In either case, being able to verify activity on the Bumbu fault would raise Lae’s earthquake risk to a new level.</p>
<h2>Future work</h2>
<p>The Lae Earthquake Risk Project is ongoing. In addition to more GPS measurements of ground motion, it will involve setting up earthquake-monitoring stations in Lae, and advanced satellite-based radar analysis. The latter should provide a much more detailed picture of which fault segments are active.</p>
<p>Once we know which active segments can produce earthquakes, we can begin to estimate the intensity of shaking these earthquakes may cause in Lae – and what effects they may have on the city’s built environment. </p>
<p>This will hopefully provide specific guidance for constructing new buildings in Lae, and strengthening existing ones. These are the most important steps that can be taken to reduce the impact of future earthquakes.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/australia-is-no-stranger-to-earthquakes-yet-our-planning-polices-have-not-adapted-168470">Australia is no stranger to earthquakes, yet our planning polices have not adapted</a>
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<img src="https://counter.theconversation.com/content/185708/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Phil Cummins works for Geoscience Australia. The National Earthquake Hazard Assessment of PNG and Lae Earthquake Risk projects are funded by the Department of Foreign Affairs and Trade (DFAT).</span></em></p><p class="fine-print"><em><span>Hadi Ghasemi works for Geoscience Australia. The National Earthquake Hazard Assessment of PNG and Lae Earthquake Risk Assessment projects are funded by the Department of Foreign Affairs and Trade (DFAT).</span></em></p>Oral histories talk about a major tectonic event 250 years ago, which changed the course of a river flowing through Lae today.Phil R. Cummins, Professor, Geoscience AustraliaHadi Ghasemi, Senior Seismologist, Geoscience AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1746852022-01-20T13:45:43Z2022-01-20T13:45:43ZShakeAlert earthquake warnings can give people time to protect themselves – but so far, few have actually done so<figure><img src="https://images.theconversation.com/files/441762/original/file-20220120-9372-1yk59g7.jpg?ixlib=rb-1.1.0&rect=122%2C644%2C3143%2C2029&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An app can give you a few seconds of warning before an earthquake strikes.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-nations-first-statewide-earthquake-early-warning-system-news-photo/1176500973?adppopup=true">Yichuan Cao/NurPhoto via Getty Images</a></span></figcaption></figure><p>My Facebook feed exploded shortly after noon on Dec. 20, 2021, with news from friends and family in northern California: A “big one!” The 6.2 magnitude earthquake they’d just experienced had its <a href="https://earthquake.usgs.gov/earthquakes/eventpage/ew1640031020/executive">epicenter on the coast near Petrolia</a>.</p>
<p>Yet many social media posts weren’t focused on the earthquake itself, but rather the <a href="https://www.theguardian.com/us-news/2021/dec/21/california-earthquake-early-warning-system">alert</a> sent to cellphones seconds before – or, for some, just as – major shaking began.</p>
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<a href="https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="screenshot of Facebook post about receiving an alert" src="https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=266&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=266&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=266&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=335&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=335&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441349/original/file-20220118-19-ygofp9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=335&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Lots of people justifiably marveled at the alert, but few seem to have taken advantage of it.</span>
<span class="attribution"><span class="source">Facebook screenshot via Dare Baldwin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><a href="https://www.usgs.gov/programs/earthquake-hazards/early-warningshakealertr">The ShakeAlert system</a> is a remarkable technology, years in the making. It has the potential to save tens of thousands of lives in areas where high-magnitude earthquakes occur by providing a few seconds’ warning – enough time for people to take basic safety precautions. Marvelous as it is, though, ShakeAlert saves lives only if people understand what to do when they receive such an alert – and do it.</p>
<p>I’m part of an interdisciplinary group that includes <a href="https://scholar.google.com/citations?user=pS-idGwAAAAJ&hl=en&oi=ao">psychologists like me</a> and other social scientists, natural hazards experts, seismologists, geophysicists and communication and education specialists whose goal is to design <a href="https://doi.org/10.1190/geo2021-0222.1">earthquake preparedness and response systems that optimize safe outcomes</a>. Some of us are working together to analyze video footage of various earthquakes posted to social media sites, such as Facebook, Twitter and YouTube.</p>
<p>Videos during the Petrolia-centered earthquake are the first we’ve seen of what people do – or don’t do – when they receive a ShakeAlert-powered alert. The footage suggests we have more work to do.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="still of surveillance footage from a hotel" src="https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441568/original/file-20220119-21-1e940uy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">CCTV footage, like this still from video taken in Jakarta, Indonesia, during the 2004 earthquake, reveals how people really respond during shaking.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/this-video-grab-from-metro-tv-in-jakarta-shows-a-hotel-cctv-news-photo/51893889">AFP/AFP via Getty Images</a></span>
</figcaption>
</figure>
<h2>Detection and warning of imminent earthquakes</h2>
<p>ShakeAlert depends on a massive network of seismic detectors distributed around the West Coast that pick up initial earthquake shaking.</p>
<p>For people near the epicenter, the time it takes to process the data and send an alert may mean it arrives just as, or possibly even seconds after, major shaking begins. Even this roughly simultaneous notice is valuable, as it helps people realize what is happening, which often isn’t obvious.</p>
<p>For those further away from a quake’s epicenter, an alert may arrive seconds, or even tens of seconds, before strong shaking. That’s enough time to automatically shut down or alter the operations of key systems – for example, to slow or stop trains, control equipment involved in delicate medical procedures, or electrical grids. It’s also enough time to prepare mentally, as well as to take potentially life-saving protective action.</p>
<p>To maximize your chances of <a href="https://www.usgs.gov/faqs/what-should-i-do-during-earthquake">coming out of a major earthquake alive and intact</a>, most experts recommend in most cases – for California, Oregon and Washington – that you “Drop, Cover, and Hold On,” or DCHO for short. The alert message appearing on your cellphone reminds you what to do.</p>
<p>ShakeAlert is the only earthquake early warning system for the public in the U.S. It <a href="https://www.oregonlive.com/environment/2021/02/earthquake-warning-system-shakealert-coming-to-oregon-in-march.html">went live in Oregon in March 2021</a>, and in May it expanded to the entire U.S. West Coast. The system sends alerts via <a href="https://www.usgs.gov/faqs/how-do-i-sign-shakealertr-earthquake-early-warning-system">a group of delivery partners</a>. For instance, Google Android phones display alerts via their operating system. Depending where people live, they can install alert apps – MyShake, QuakeAlert USA or San Diego Emergency ShakeReadySD – to their smartphone. And the Federal Emergency Management Agency system that sends emergency messages like Amber Alerts also issues earthquake warnings.</p>
<p>Considerable prior <a href="https://doi.org/10.1016/j.ijdrr.2020.101713">research helped to shape the content</a> conveyed in ShakeAlert-powered alerts, as well as key messaging that occurs right after alerts. Getting all of this right is crucial, and it’s still a work in progress.</p>
<h2>What people do before and during quakes</h2>
<p>Until recently, researchers have had to rely primarily on after-the-fact interviews or “<a href="https://earthquake.usgs.gov/data/dyfi/">Did You Feel It?</a>” post-earthquake surveys to learn what people remembered doing during an earthquake.</p>
<p>In the last several years, closed-circuit TV footage has started to reveal how people really respond to high-intensity shaking. These recordings aren’t muddled by individuals’ understandably imperfect memories of a chaotic and stressful event. Though people frequently report having taken protective actions such as “Drop, Cover, and Hold On” during an earthquake, analyses of CCTV footage to date show that DCHO is, as yet, actually quite rare.</p>
<p>There are a few encouraging exceptions, though. For instance, CCTV footage from the 2018 7.2 magnitude earthquake in Anchorage, Alaska, shows a teacher and students in <a href="https://www.adn.com/alaska-news/anchorage/2018/12/04/this-classroom-footage-captures-anchorage-students-reacting-perfectly-to-the-earthquake/">one middle-school classroom collectively enacting DCHO</a> immediately and flawlessly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="seated person holds up cell phone to show a person who looks shocked" src="https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441528/original/file-20220119-23-3ltaat.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A still from CCTV footage just before the Petrolia earthquake seems to depict people astonished by the ShakeAlert warning, but taking no action.</span>
<span class="attribution"><span class="source">Screen grab from Earth Quake Video World</span></span>
</figcaption>
</figure>
<p>The Petrolia earthquake videos offer the first chance to see if ShakeAlert-powered messages change how people behave before, during and even after a major earthquake. So far, in the footage we’ve seen, people noticed the alert yet did nothing relevant to protecting themselves.</p>
<p>In fact, no one in any of these videos from Dec. 20 undertook “Drop, Cover, and Hold On” precautions, regardless of whether, or when, they received an alert. Many people just stayed where they were, showed the alert on their phones to others and excitedly watched as objects swayed and crashed to the floor.</p>
<h2>Frozen in the face of an emergency</h2>
<p>My colleagues and I are hoping that a better understanding of what people actually do during major earth shaking will suggest ways to tweak the alerts so they inspire people to take safer actions. It’s a big challenge because doing nothing when an earthquake begins appears to be very common.</p>
<p>A 2021 survey conducted in both Seattle and Sendai, Japan, found that stopping and staying put was the <a href="https://doi.org/10.1016/j.ijdrr.2021.102624">dominant response to major earth shaking</a>, even though it puts people at risk of serious injury from falling or being hit by falling objects. There are several likely reasons.</p>
<p>A major earthquake is a novel experience for many people, and often they simply may not know what to do. In addition, there are potential barriers to carrying out “Drop, Cover, and Hold On.” Age, disability and high body mass can make dropping to the floor and getting under cover problematic, though there are <a href="https://ars.els-cdn.com/content/image/1-s2.0-S2212420918313888-gr1_lrg.jpg">inclusive ways to DCHO</a>.</p>
<p>[<em>Over 140,000 readers rely on The Conversation’s newsletters to understand the world.</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-140ksignup">Sign up today</a>.]</p>
<p>Even when people do know what to do in an emergency, evidence suggests they may feel self-conscious or <a href="https://doi.org/10.1016/j.ijdrr.2019.101150">embarrassed about taking action</a>. Classic social science research points to <a href="https://doi.org/10.1016/0022-1031(72)90069-8">how contagious it can be</a>, in the face of a variety of emergencies, to do nothing, creating cascading paralysis for everyone present.</p>
<p>By dropping, covering and holding on right when you receive an alert, you might unleash similar protective action in others nearby, possibly saving them, as well as yourself, from injury or death. Seen that way, doing DCHO when you receive an alert – despite the potential for embarrassment – is actually a form of everyday heroism.</p><img src="https://counter.theconversation.com/content/174685/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dare A. Baldwin, Ph.D., is a Full Professor at the University of Oregon; her research at the University of Oregon is supported in part by the United States Geological Survey.</span></em></p>When researchers look at CCTV footage of how people really react during earthquakes – as opposed to what they report after the fact – it looks like alerts aren’t yet inspiring protective action.Dare A. Baldwin, Full Professor, Psychology and Clark Honors College, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1492072020-11-10T18:02:46Z2020-11-10T18:02:46ZOil field operations likely triggered earthquakes in California a few miles from the San Andreas Fault<figure><img src="https://images.theconversation.com/files/368060/original/file-20201106-19-1pzp43f.jpg?ixlib=rb-1.1.0&rect=122%2C1226%2C2013%2C1211&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Activity in the San Ardo oil field near Salinas, California, has been linked to earthquakes.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:USA-San_Ardo-Oil_Fields-5.jpg">Eugene Zelenko/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The way companies drill for oil and gas and dispose of wastewater can trigger earthquakes, at times in unexpected places.</p>
<p>In West Texas, earthquake rates are now <a href="http://doi.org/10.1029/2019JB018558">30 times higher</a> than they were in 2013. Studies have also linked earthquakes to oil field operations in <a href="http://doi.org/10.1126/sciadv.1601542">Oklahoma</a>, <a href="http://doi.org/10.1002/2017GL076334">Kansas</a>, <a href="https://doi.org/10.1785/0120140009">Colorado</a> and <a href="https://doi.org/10.1785/0120140168">Ohio</a>.</p>
<p>California was thought to be an exception, a place where oil field operations and tectonic faults apparently coexisted without much problem. Now, new research shows that the state’s natural earthquake activity may be hiding industry-induced quakes.</p>
<p>As <a href="http://www.ceri.memphis.edu/people/thgoebel/">a seismologist</a>, I have been investigating induced earthquakes in the U.S., Europe and Australia. Our <a href="https://doi.org/10.1785/0220200276">latest study</a>, released on Nov. 11, shows how California oil field operations are putting stress on tectonic faults in an area just a few miles from the San Andreas Fault. </p>
<h2>Seismic surge</h2>
<p>Industry-induced earthquakes have been an increasing concern in the central and eastern United States for more than a decade.</p>
<p>Most of these earthquakes are too small to be felt, but not all of them. In 2016, a magnitude 5.8 earthquake damaged buildings in Pawnee, Oklahoma, and led state and federal regulators to <a href="https://apnews.com/article/612b2303f71641f388b0224fb6dab557">shut down 32 wastewater disposal wells</a> near a newly discovered fault. Large earthquakes are rare far from tectonic plate boundaries, and Oklahoma experiencing three magnitude 5 or greater earthquakes in one year, as happened in 2016, was unheard of.</p>
<p><iframe id="iHe4g" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/iHe4g/4/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Oklahoma’s earthquake frequency fell with lower oil prices and regulators’ decision to require companies to <a href="http://doi.org/10.1126/sciadv.1601542">decrease their well injection volume</a>, but there are still more earthquakes there today than in 2010. </p>
<p>A familiar pattern has been emerging in West Texas in the past few years: drastically increasing earthquake rates well beyond the natural rate. A <a href="https://earthquake.usgs.gov/earthquakes/eventpage/us70008ggn/executive">magnitude 5 earthquake</a> shook West Texas in March. </p>
<p><iframe id="Y7K37" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/Y7K37/4/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>How it works</h2>
<p>At the root of the induced earthquake problem are two different types of fluid injection operations: hydraulic fracturing and wastewater disposal.</p>
<p>Hydraulic fracturing involves injecting water, sand and chemicals at very high pressures to create flow pathways for hydrocarbons trapped in tight rock formations. Wastewater disposal involves injecting fluids into deep geological formations. Although wastewater is pumped at low pressures, this type of operation can disturb natural pressures and stresses over large areas, several miles from injection wells.</p>
<figure class="align-center ">
<img alt="illustration of fracking, oil recovery and wastewater disposal." src="https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=986&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=986&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=986&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1239&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1239&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368106/original/file-20201108-23-h53elw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1239&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/oil-production-and-wastewater-disposal">U.S. Geological Survey</a></span>
</figcaption>
</figure>
<p>Tectonic faults underneath geothermal and oil reservoirs are often precariously balanced. Even a small perturbation to the natural tectonic system – due to deep fluid injection, for example – can <a href="https://science.sciencemag.org/content/360/6392/1007">cause faults to slip and trigger earthquakes</a>.
The consequences of fluid injections are easily seen in Oklahoma and Texas. But what are the implications for other places, such as California, where earthquake-prone faults and oil fields are located in close proximity?</p>
<h2>California oil fields’ hidden risk</h2>
<p>California provides a particularly interesting opportunity to study fluid injection effects.</p>
<p>The state has a large number of oil fields, earthquakes and many <a href="https://maps.conservation.ca.gov/doggr/wellfinder/#openModal">instruments</a> <a href="https://maps.conservation.ca.gov/cgs/fam/">that detect even tiny events</a>, and it was thought to be <a href="https://pubs.geoscienceworld.org/bssa/article-lookup/64/3-1/699">largely free</a> of unnatural earthquakes.</p>
<p>My colleague Manoo Shirzaei from Virginia Tech and I wondered if induced earthquakes could be masked by nearby natural earthquakes and were thus missed in previous studies. </p>
<p>We conducted a <a href="https://doi.org/10.1785/0220200276">detailed seismologic study</a> of the Salinas basin in central California. The study area stands out because of its proximity to the San Andreas Fault and because waste fluids are injected at high rates close to seismically active faults. </p>
<figure class="align-center ">
<img alt="Satellite hot-spot image showing rising ground." src="https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368028/original/file-20201106-23-kdg39n.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Satellite data shows the ground rising as much as 1.5 centimeters per year in parts of the San Ardo oil field. The line-of-sight velocity (LOS-VEL), as viewed from the satellite, shows how rapidly the ground surface is rising.</span>
<span class="attribution"><span class="source">Thomas Goebel/University of Memphis</span></span>
</figcaption>
</figure>
<p>Using satellite radar images from 2016 to 2020, Shirzaei made a surprising observation: Some regions in the Salinas basin were lifting at about 1.5 centimeters per year, a little over half an inch. This uplift was a first indication that fluid pressures are out of balance in parts of the San Ardo oil field. Increasing fluid pressures in the rock pores stretch the surrounding rock matrix like a sponge that is pumped full of water. The resulting reservoir expansion elevates the forces that act on the surrounding tectonic faults.</p>
<p>Next, we examined the seismic data and found that fluid injection and earthquakes were highly correlated over more than 40 years. Surprisingly, this extended out 15 miles from the oil field. Such distances are similar to the large spatial footprint of injection wells in Oklahoma. We analyzed the spatial pattern of 1,735 seismic events within the study area and found clustering of events close to injection wells.</p>
<figure class="align-center ">
<img alt="Map of wells and earthquakes." src="https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=493&fit=crop&dpr=1 600w, https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=493&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=493&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=619&fit=crop&dpr=1 754w, https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=619&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/367957/original/file-20201106-17-a7y4f.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=619&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The stresses from injecting water can trigger earthquakes several miles from the well itself. The blue triangles scale with each well’s injection rate.</span>
<span class="attribution"><span class="source">Thomas Goebel/University of Memphis</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Other areas in California may have a similar history, and more detailed studies are needed to differentiate natural from induced events there.</p>
<h2>How to lower the earthquake risk</h2>
<p>Most wastewater disposal and hydraulic fracturing wells do not lead to earthquakes that can be felt, but the wells that cause problems have three things in common:</p>
<ul>
<li>These are high-volume injection wells;</li>
<li>They inject into highly permeable rock formations; and </li>
<li>These formations are located directly above tectonic faults in the <a href="http://doi.org/10.1126/science.aap7911">deeper geologic basement</a>.</li>
</ul>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>Although the first issue may be difficult to resolve because reducing the volume of waste fluids would require reducing the amount of oil produced, the locations of injection wells can be planned more carefully. The seismic safety of oil and gas operations may be increased by selecting geologic formations that are disconnected from deep faults.</p>
<p><em>This article has been updated with a link to the study.</em></p><img src="https://counter.theconversation.com/content/149207/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas H. Goebel receives funding from the U.S. Department of Energy</span></em></p>California was thought to be an exception, a place where oil field operations and tectonic faults apparently coexisted without much problem. Not any more.Thomas H. Goebel, Assistant Professor, University of MemphisLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1432032020-07-23T18:04:37Z2020-07-23T18:04:37ZCoronavirus lockdown reduced seismic activity around the world – new study<p>Seismic activity doesn’t just come from earthquakes, volcanoes and landslides. Everyday human activity also gives rise to vibrations that travel through the ground as seismic waves, something we call “anthropogenic noise”.</p>
<p>When pandemic lockdown measures brought daily life to a standstill, it didn’t just change life at the surface and <a href="https://www.nature.com/articles/s41558-020-0797-x">cut emissions</a> into the atmosphere. It also reduced anthropogenic noise beneath our feet, particularly in urban environments. Our new study, <a href="https://science.sciencemag.org/lookup/doi/10.1126/science.abd2438">published in Science</a>, is the first to analyse these changes at a global scale and shows a near-simultaneous reduction of this seismic noise around the world.</p>
<p>We found that seismic noise dropped by an average of 50% in 77 countries between March and May 2020. The seismic lockdown effect was even observed in remote areas and in boreholes several hundred metres below the ground. </p>
<p>These changes correlated with independent estimates of the reduction in human activity. This implies that we could use publicly available seismic data to track the effectiveness of lockdown measures and how quickly countries are returning to normal once measures are lifted.</p>
<p>We can record vibrations travelling through the ground using sensitive scientific instruments called seismometers. Traditionally, these are located in quiet places, away from urban areas. This is because the high-frequency vibrations from humans at the surface, which create a sort of high-pitched buzz, contaminate our data and make it harder to monitor natural events such as earthquakes and volcanoes.</p>
<p>Besides the thousands of high-end professional monitoring stations around the world, networks of citizen-science sensors <a href="https://raspberryshake.net/stationview/">have rapidly grown</a> in the last few years, installed by individuals and schools. These often operate in more urban settings, with data generally shared openly with a global community of seismologists.</p>
<p>Our study was spawned after the lead author, seismologist <a href="https://www.geophysique.be/thomas-lecocq/">Thomas Lecocq</a> of the Royal Observatory of Belgium, decided that the best way to tackle the problem of efficiently analysing data from all around the globe was to <a href="https://github.com/ThomasLecocq/SeismoRMS">share his method</a> with the seismological community. </p>
<p>This started a team effort to download, process and analyse the many terabytes of data available from sensors and monitoring stations, resulting in a unique collaboration involving 76 authors from 66 institutions in 27 countries. This global community, together with the principles of open data and sharing science have been crucial for our study to take place in such a short time span.</p>
<h2>The seismic lockdown wave</h2>
<p>By analysing months- to years-long datasets from over 300 seismic stations around the world, our study was able to show that seismic noise was reduced in many countries. This made it possible to visualise the resulting “seismic lockdown wave” moving through China at the end of January, to Italy in March, and then around the rest of the world. While 2020 has not seen a reduction in earthquakes, this seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record.</p>
<p>The largest drops in seismic noise were seen in the most densely populated areas, such as Singapore and New York City. But the reduction was also observed in quieter locations such as Germany’s Black Forest and the small city of Rundu in Namibia. Particularly large drops were observed in data taken from around schools and universities.</p>
<p>There was a strong match between how much seismic noise fell in a particular area and the change in the amount of human movement recorded there, as measured using mobile phone data made publicly available by <a href="https://www.google.com/covid19/mobility/">Google</a> and <a href="https://www.apple.com/covid19/mobility">Apple</a>). This correlation means open seismic data can act as a broad proxy for tracking human activity almost as it happens – as people reduce their movements, seismic noise quickly decreases. We can also use the seismic data to understand the effects of pandemic lockdowns and recoveries without impinging on people’s privacy because we don’t rely on the movements of individuals.</p>
<p>More broadly, the seismic lockdown will help us to differentiate between human and natural causes of seismic noise. The gradual easing of restrictions will allow us to monitor the effect of different human activities on seismic noise and lead to a better understanding of anthropogenic noise sources.</p>
<p>The reduction in seismic noise also gives us the opportunity to listen in to the Earth’s natural vibrations without the distortions of human input. We have reported on the first evidence that previously concealed earthquake signals, especially during the daytime, appeared much more clearly on seismometers in urban areas during lockdown. We hope that our work will lead to <a href="https://www.solid-earth.net/special_issues/schedule.html">further research</a> on the seismic lockdown with the aim of hunting for previously hidden signals from earthquakes and volcanoes.</p><img src="https://counter.theconversation.com/content/143203/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paula Koelemeijer receives funding from The Royal Society. </span></em></p><p class="fine-print"><em><span>Stephen Hicks does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Measuring seismic noice could show whether people are following future lockdown measures.Paula Koelemeijer, Royal Society University Research Fellow, Royal Holloway University of LondonStephen Hicks, Postdoctoral Research Associate in Seismology, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1170052019-05-21T19:40:28Z2019-05-21T19:40:28ZThe ‘pulse’ of a volcano can be used to help predict its next eruption<figure><img src="https://images.theconversation.com/files/274836/original/file-20190516-69178-x4wstq.jpg?ixlib=rb-1.1.0&rect=0%2C645%2C4031%2C2372&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The 2018 eruption of Kilauea volcano was preceded by damage of the magma plumbing system at the summit.</span> <span class="attribution"><span class="source">Courtesy of Grace Tobin, 60 Minutes</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Predicting when a volcano will next blow is tricky business, but <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081609" title="Decrease in Seismic Velocity Observed Prior to the 2018 Eruption of Kīlauea Volcano With Ambient Seismic Noise Interferometry">lessons we learned</a> from one of Hawaii’s recent eruptions may help.</p>
<p><a href="https://theconversation.com/au/topics/kilauea-53358">Kīlauea</a>, on the Big Island of Hawai'i, is probably the best understood volcano on Earth. That’s thanks to monitoring and gathered information that extends back to the formation of the <a href="https://volcanoes.usgs.gov/observatories/hvo/">Hawaiian Volcano Observatory</a> in 1912.</p>
<p>The volcano is also subject to the world’s most technologically advanced geophysical monitoring network.</p>
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<a href="https://theconversation.com/from-kilauea-to-fuego-three-things-you-should-know-about-volcano-risk-97775">From Kilauea to Fuego: three things you should know about volcano risk</a>
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<p>From the skies, satellites collect data that show the changing topography of the volcano as magma moves throughout the internal magma plumbing system. Satellites also look at the composition of volcanic gases. </p>
<p>From the ground, volcanologists use a number of highly sensitive chemical and physical tools to further understand the structure of that magma plumbing system. This helps to study the movement of magma within the volcano.</p>
<h2>Earthquakes and vibrations</h2>
<p>A lynch pin of volcano monitoring is seismicity – how often, where and when earthquakes occur. Magma movement within the volcano triggers earthquakes, and putting together the data on their location (a technique known as triangulation) tracks the path of magma underground.</p>
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<a href="https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=215&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=215&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=215&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=271&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=271&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274839/original/file-20190516-69178-wpysqy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=271&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A schematic of the deep magma plumbind system of Kilauea volcano, Big Island, Hawaii. Magma is transported from deep within the Earth and arrives in a series of summit magma reservoirs.</span>
<span class="attribution"><span class="source">USGS</span></span>
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<p>A newer technique, seismic interferometry, uses vibrations of energy from ocean waves hitting the distant shorelines that then travel through the volcano.</p>
<p>Changes in the speed of these vibrations help us map the 3D footprint of the volcano’s magma plumbing system. We can then detect when, and in some cases how, the magma plumbing system is changing.</p>
<p>This monitoring provides the “pulse” of the volcano during times of inactivity - a baseline from which to detect change during volcanic unrest. This proved invaluable for early warning, and the prediction of where and when, of the eruption of Kīlauea on May 3, 2018.</p>
<p>The “pulse” of Kīlauea includes cycles of <a href="https://volcanoes.usgs.gov/observatories/hvo/hvo_volcano_watch.html?vwid=117">volcano inflation (bulging) and deflation (contraction)</a> as magma moves into and out of the storage region at the summit of the volcano.</p>
<p>The speeds of vibrations travelling through the volcano are predictable during observations of inflation/deflation cycles. When the volcano bulges, the vibrations travel faster through the volcano as rock and magma is compressed. When the volcano contracts these speeds decrease.</p>
<p>We describe this relationship between the two sets of data – the bulging/contraction and the faster/slower speed of vibrations – as coupled.</p>
<h2>Something changed</h2>
<p>Compared to our baseline, we saw the coupled data shift 10 days before the Kīlauea eruption on May 3. That told scientists the magma plumbing system had changed in a significant way.</p>
<p>The volcano was bulging due to the buildup of pressure inside the magma chamber, but the seismic waves were slowing down quite dramatically, instead of speeding up. </p>
<p>Our interpretation of this data was that the summit magma chamber was not able to sustain the pressure from an increasing magma supply – the bulge was too big. Rock material started to break around the summit magma chamber.</p>
<p>Breakage of the rocks perhaps then led to changes of the summit magmatic system so that more magma could more easily arrive at the eruption site about 40km away.</p>
<p>As well as Kīlauea, such coupled data sets are regularly collected, investigated and interpreted in terms of magma transport at other volcanoes globally. Sites include Piton de la Fournaise on Reunion Island, and Etna volcano, Italy. </p>
<p>But our <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081609">modelling</a> was the first to demonstrate these changes in the coupled data relationship could occur due to weakening of the material inside the volcano before an eruption.</p>
<p>The damage model that we applied can now be used for other volcanoes in a state of unrest. This adds to the toolbox volcanologists need to predict the when and where of an impending eruption. </p>
<h2>So much data, we need help</h2>
<p>When volcanoes are in a heightened state of unrest, the volume of information available from digital data and ground observations is extreme. Scientists tend to rely on observational monitoring first, and other data when time and extra people are available. </p>
<p>But the total amount of incoming data (such as from satellites) is overwhelming, and scientists simply can’t keep up. Machine learning might be able to help us here. </p>
<p><a href="https://www.sciencemag.org/news/2018/12/artificial-intelligence-helps-predict-volcanic-eruptions">Artificial intelligence</a> is the new kid on the block for eruption prediction. Neural networks and other algorithms can use high volumes of complex data and “learn” to distinguish between different signals.</p>
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Read more:
<a href="https://theconversation.com/how-the-dinosaurs-went-extinct-asteroid-collision-triggered-potentially-deadly-volcanic-eruptions-112134">How the dinosaurs went extinct: asteroid collision triggered potentially deadly volcanic eruptions</a>
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<p><a href="https://www.nature.com/articles/d41586-018-07420-y">Automated early alert systems</a> of an impending eruption using sensor arrays exist for some volcanoes today, for example at Etna volcano, Italy. It’s likely that artificial intelligence will make these systems more sophisticated in the future.</p>
<p>Early detection sounds wonderful for authorities charged with public safety, but many volcanologists are wary.</p>
<p>If they lead to multiple false alarms then that could slash trust in scientists for both managers of volcanic crises and the public alike.</p><img src="https://counter.theconversation.com/content/117005/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rebecca Carey receives funding from the Australian Research Council, US National Science Foundation and New Zealand Marsden Grant.</span></em></p>Scientists say they’ve found a new method to help predict when volcanoes will erupt, based on data crunched from an eruption last year in Hawaii.Rebecca Carey, Senior Lecturer in Earth Sciences, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1042652018-10-04T09:53:11Z2018-10-04T09:53:11ZIndonesia tsunami: why wasn’t there an earlier warning?<p>The recent earthquake and tsunami in Indonesia has claimed the lives of <a href="https://www.bbc.co.uk/news/world-asia-45716915">at least 1,350 people</a>. Many more people are missing and the disaster has destroyed homes and businesses across the city of Palu and surrounding area on the island of Sulawesi.</p>
<p>Yet after the much larger tsunami that devastated countries around the Indian Ocean in 2004, Indonesia began installing a <a href="https://news.nationalgeographic.com/news/2014/12/141226-tsunami-indonesia-catastrophe-banda-aceh-warning-science">new early warning system</a> to try to prevent such widespread destruction from happening again. So why is the country once again facing such a severe loss of life? The location of the tsunami may have made the destruction particularly acute, but the country’s early warning system also appears not to have lived up to expectations.</p>
<p>A tsunami (Japanese for “harbour wave”) <a href="https://www.tsunami-alarm-system.com/en/content/phaenomen-tsunami-entstehung">is formed</a> when a disturbance on the sea floor leads to a series of large waves which spread out across the ocean. This disturbance can be caused by a large earthquake, an underwater landslide, or even <a href="http://itic.ioc-unesco.org/index.php?option=com_content&view=article&id=1159:how-do-volcanic-eruptions-generate-tsunamis&catid=1340&Itemid=2059">a volcanic eruption</a>.</p>
<p>When the tsunami waves reach shallow water as they move towards the shore, the speed of the wave slows down and causes the water to dramatically pile up. The increase in wave height leads to devastating coastal flooding especially in highly populated, low-lying areas.</p>
<p>The height of the wave depends on the size of the tsunami wave but also by the shape of the coastline. For example, tsunamis will have a greater impact where the wave moves through a narrow, elongated bay, like Palu, as it approaches the shore. The earthquake in Sulawesi likely disturbed sediments on the seabed and triggered a local underwater landslide. These two factors combined could explain the six-metre waves that reached Palu. </p>
<p>More than one wave can occur during a tsunami, meaning that such events can continue to impact the coastline over a number of hours. It can be the case that the second, third or even later waves can be the biggest.</p>
<h2>Early warning systems</h2>
<p>Unfortunately it isn’t possible to predict exactly when a tsunami may strike a coastal area, but there are clues that can save lives. Indonesia’s main early warning system is made up of a network of tidal gauges that measure sea level, and land-based stations that detect earthquake activity. However, the tidal gauges were <a href="https://www.nytimes.com/interactive/2018/10/02/world/asia/indonesia-tsunami-early-warning-system.html">so far away</a> from Palu that they only registered a small rise in the water level as the waves started to form. It’s possible the system wasn’t set up to take into account how the waves would grow as they travelled down Palu’s bay.</p>
<p>A more <a href="https://oceantoday.noaa.gov/trackingtsunamis/">advanced warning system</a> is more common in some areas of the world affected by tsunamis and earthquakes, using a series of buoys in the sea to detect any movement of the seafloor. In the event of a tsunami, the buoys send a signal to the local agency responsible for issuing a clear advance warning to coastal residents to allow people to get to higher ground away from the advancing waters.</p>
<p>Indonesia has installed a new sea-based system but some researchers <a href="https://www.nytimes.com/aponline/2018/09/30/world/asia/ap-as-indonesia-tsunamis.html">have said</a> that it is stuck in the testing phase, and that the ocean buoys deployed aren’t working properly. They point to a potential life-saving early warning system hampered by lack of funding and delays, despite the very real threat from tsunamis in this part of the world following the 2004 event.</p>
<p>There may have also been a problem with the way the information about the incoming waves was used. The Indonesian authorities in this case did issue a tsunami warning via text message, but the earthquake destroyed <a href="https://www.nytimes.com/2018/09/29/world/asia/indonesia-tsunami-sulawesi-palu.html">many cellphone towers</a>. Similarly, damage to power lines <a href="https://www.nytimes.com/aponline/2018/09/30/world/asia/ap-as-indonesia-tsunamis.html">reportedly prevented</a> sirens from working. The authorities have also been accused of cancelling the warning too soon.</p>
<p>Unfortunately, Sulawesi has paid the price for an incomplete tsunami warning system as well underestimating the wave heights that actually struck the coastline.</p><img src="https://counter.theconversation.com/content/104265/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sue Dawson receives funding from the Natural Environmental research Council </span></em></p>The early warning system installed after the 2004 Boxing Day tsunami hasn’t lived up to expectations.Sue Dawson, Reader in Physical Geography, University of DundeeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1014992018-08-15T11:33:38Z2018-08-15T11:33:38ZIndonesia earthquake: how scrap tyres could stop buildings collapsing<figure><img src="https://images.theconversation.com/files/232066/original/file-20180815-2891-6hbtvz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Collapsed building after 2018 Lombok earthquake.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/indonesia-lombok-august-9-2018-buildings-1154843722?src=er3k8KiQs_MtOYxhU-AM-w-1-0">Shutterstock</a></span></figcaption></figure><p>At the time of writing, <a href="https://www.cnn.com/2018/08/13/asia/lombok-earthquake-intl/index.html">436 people have died</a> following an earthquake in the Indonesian island of Lombok. A further 2,500 people have been hospitalised with serious injuries and over 270,000 people have been displaced.</p>
<p>Earthquakes are one of the deadliest natural disasters, accounting for just 7.5% of such events between 1994 and 2013 but causing <a href="https://www.emdat.be/sites/default/files/adsr_2016.pdf">37% of deaths</a>. And, as with all natural disasters, it isn’t the countries that suffer the most earthquakes that see the biggest losses. Instead, the number of people who die in an earthquake is related to <a href="https://www.cred.be/downloadFile.php?file=sites/default/files/PubID266Earthquakes.pdf">how developed</a> the country is.</p>
<p>In Lombok, as <a href="https://edition.cnn.com/2015/05/10/asia/nepal-earthquake-death-toll/">in Nepal in 2015</a>, many deaths were caused by the widespread collapse of local rickety houses incapable of withstanding the numerous aftershocks. More generally, low quality buildings and inadequate town planning are the <a href="https://www.emdat.be/sites/default/files/adsr_2016.pdf">two main reasons</a> why seismic events are more destructive in developing countries.</p>
<p>In response to this issue, my colleagues and I are working on a way to create cheap building foundations that are better at absorbing seismic energy and so can prevent structures from collapsing during an earthquake. And the key ingredient of these foundations is rubber from scrap tyres, which are otherwise very difficult to safely dispose of and are largely <a href="https://www.thehindu.com/business/Turning-waste-tyre-into-%25E2%2580%2598green-steel%25E2%2580%2599/article14518524.ece">sent to landfill</a> or burnt, releasing large amounts of carbon dioxide and toxic gases containing heavy metals. </p>
<h2>Rubber-soil mixture</h2>
<p>Previous attempts to protect buildings from earthquakes by altering their foundations have shown promising results. For example, a recently developed underground <a href="https://theconversation.com/our-new-anti-earthquake-technology-could-protect-cities-from-destruction-44028">vibrating barrier</a> can reduce between 40% and 80% of surface ground motion. But the vast majority of these sophisticated isolation methods are expensive and very <a href="https://www.researchgate.net/publication/263556747_Seismic_isolation_for_low-to-medium-rise_buildings_using_granulated_rubber-soil_mixtures_Numerical_study">hard to install</a> under existing buildings.</p>
<p>Our alternative is to create foundations made from local soil mixed with some of the <a href="http://www.etrma.org/uploads/Modules/Documentsmanager/elt-report-v9a---final.pdf">15m tonnes</a> of scrap tyre produced annually. This rubber-soil mixture can reduce the effect of seismic vibrations on the buildings on top of them. It could be easily retrofitted to existing buildings at low cost, <a href="https://www.researchgate.net/publication/262894408_Seismic_isolation_using_granulated_tire-soil_mixtures_for_less-developed_regions_Experimental_validation">making it particularly suitable for developing countries</a>. </p>
<p><a href="https://www.researchgate.net/publication/234720015_Dynamic_properties_of_dry_sandrubber_SRM_and_gravelrubber_GRM_mixtures_in_a_wide_range_of_shearing_strain_amplitudes">Several investigations</a> have shown that introducing rubber particles into the soil can increase the amount of <a href="https://www.researchgate.net/publication/326573152_Dynamic_behaviour_of_shredded_rubber_soil_mixtures">energy it dissipates</a>. The earthquake causes the rubber to deform, absorbing the energy of the vibrations in a similar way to how the outside of a car <a href="https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/crumple-zone.htm">crumples in a crash</a> to protect the people inside it. The stiffness of the sand particles in the soil and the friction between them helps maintain the consistency of the mixture.</p>
<p>My colleagues and I <a href="https://www.researchgate.net/project/The-use-of-rubber-sand-mixtures-RSM-for-the-mitigation-of-earthquake-damage-in-structures?_sg=Lt6JDvLryAwjsLhMrpPu5DZ0IhUMO5LKobDzL6YDAfcF_Rc6ZYA0HGAabGeV10GzT_hRYcIgZkjne9GrWuYGGID_b_hsxIjSiJ5-">have shown</a> that introducing rubber-soil mixture can also change the natural frequency of the soil foundation and how it interacts with the structure above it. This could help avoid a well-known resonance phenomenon that occurs when the seismic force has a similar frequency to that of the natural vibration of the building. If the vibrations match they will accentuate each other, dramatically amplifying the shake of the earthquake and causing the structure to collapse, as happened in the famous case of the <a href="http://www.wsdot.wa.gov/tnbhistory/connections/connections3.htm">Tacoma Narrows bridge in 1940</a>. Introducing a rubber-soil mixture can offset the vibrations so this doesn’t happen. </p>
<h2>A promising future</h2>
<p>The key to making this technology work is finding the optimum percentage of rubber to use. Our preliminary calculations echo <a href="https://www.researchgate.net/publication/229742536_Seismic_isolation_by_rubber-soil_mixtures_for_developing_countries">other investigations</a>, indicating that a layer of rubber-soil mixture between one and five metres thick beneath a building would reduce the maximum horizontal acceleration force of an earthquake by between 50% and 70%. This is the most destructive element of an earthquake for residential buildings. </p>
<p>We are <a href="https://www.napier.ac.uk/research-and-innovation/impact-case-studies/from-cycle-paths-to-seismic-maths">now studying how different shaped rubber-soil mixture</a> foundations could make the system more efficient, and how it is affected by different types of earthquake. Part of the challenge with this research is testing the system. We build <a href="https://youtu.be/bIqV95gIf9o">small-scale table models</a> to try to understand how the system works and assess the accuracy of computer simulations. But testing it in the real world requires an actual earthquake, and it’s almost impossible to know exactly when and where one will strike.</p>
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<p>There are ways of testing it through large scale experiments, which involve creating full-size model buildings and shaking them to simulate the force from recorded real earthquakes. But this needs funding from big institutions or companies. Then it is just a question of trying the solution on a real building by convincing the property owners that it’s worthwhile.</p><img src="https://counter.theconversation.com/content/101499/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Juan Bernal-Sanchez works for Edinburgh Napier University. </span></em></p>Researchers are using a rubber-soil mixture to make earthquake-proof foundations.Juan Bernal-Sánchez, PhD Resarcher, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1012472018-08-08T05:47:04Z2018-08-08T05:47:04ZAfter devastating earthquakes, Indonesia must embrace radical change<p>An earthquake on Lombok island in Indonesia has left 98 people dead and 20,000 people homeless, according to the <a href="https://www.washingtonpost.com/world/asia_pacific/the-latest-1000s-of-homes-damaged-in-indonesia-earthquake/2018/08/05/ade857e8-9914-11e8-a8d8-9b4c13286d6b_story.html?noredirect=on">National Disaster Mitigation Agency</a>.</p>
<p>Around 70% of North Lombok’s housing stock has either collapsed or been severely damaged. Just a week earlier, a 6.5-magnitude earthquake hit a nearby region, destroying tens of houses and claiming 10 lives, and injuring more than a dozen people.</p>
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Read more:
<a href="https://theconversation.com/two-types-of-tectonic-plate-activity-create-earthquake-and-tsunami-risk-on-lombok-101177">Two types of tectonic plate activity create earthquake and tsunami risk on Lombok</a>
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<p>As the area recovers, we need to ask: how can Indonesia address its vulnerability to earthquakes?</p>
<p>We know that Indonesia can improve its response to natural disasters, which has happened with <a href="http://doi.org/10.2312/GFZ.7.1.2017.001">tsunami preparedness</a>. The next challenge is to apply these lessons to seismic activity. </p>
<h2>Prepare for tourists</h2>
<p>Thousands of tourists were caught in panics after both earthquakes. It’s time for Indonesia’s emergency systems to address the vulnerability of foreign visitors as well as its own citizens. </p>
<p>With tourism on the rise in many earthquake-prone areas, solid preparation measures need to be put in place. Vulnerable hotels and fragile houses can jeopardise tourism’s future.</p>
<p>The past 30 years have been filled with wake-up calls. A 1992 earthquake that struck Flores island caused 15,000 houses to collapse in a single district alone. It took <a href="http://hss.ulb.uni-bonn.de/2011/2451/2451.pdf">almost 20 years for tourism to recover</a>. </p>
<h2>More technology isn’t the answer</h2>
<p>It’s often easier to attract international funding to sophisticated new technology for hazard prediction and monitoring – for example, the Australia-funded <a href="http://inasafe.org/">Inasafe</a>, which has the potential to help government to develop scenarios for better planning, preparedness and response activities, and the US-funded <a href="http://inaware.bnpb.go.id/inaware/">Inaware</a> which is a disaster management tool aimed at improving Indonesia’s risk assessment and early warning systems.</p>
<p>At the same time, it is not clear how these technological advancements will serve to help small hotels or households in earthquake-prone regions. What people really need is need help to build structures in accordance with proper construction codes, so that they don’t become death-traps during an earthquake. </p>
<p>This points to a deeper problem. Such building codes already exist, but local governments are currently showing little desire to comply with national building regulations.</p>
<p>For example, before 2011, less than 12% of local governments adopted and endorsed the <a href="http://www.bpn.go.id/PUBLIKASI/Peraturan-Perundangan/Undang-Undang/undang-undang-nomor-28-tahun-2002-2056">Building Law 2002</a>. By 2016 that figure had <a href="https://indosasters.org/endorsement-of-building-law-2002-by-local-government/">risen to 60%</a> – an improvement, but still not enough.</p>
<p>In North Lombok, where most houses collapsed in the recent earthquakes, the local government only endorsed national building regulations in 2011. It will take years for the local administrators to actually implement them.</p>
<h2>The no-regreat approach</h2>
<p>To save lives, we need to move beyond the idea that perfect risk assessment exists.</p>
<p>Seismic mitigation measures need to start immediately, at the local level. Thousands building are built every day and right now, while many are rebuilding after disaster, is the time for local governments to put into practise the codes and standards that exist at a national level. </p>
<p>Local and central governments can embrace innovation. Central government and local governments in Indonesia must focus on transforming the way houses are built, including checking earthquake preparedness when issuing building permits.</p>
<p>Can local government radically audit all vulnerable houses? And can we create a machine of local bureaucrats who can deal with the risk assessment on every single house in earthquake prone regions?</p>
<p>It may seem hard, but good practices are already available. Apart from creating incentives for local engineers, contractors, and building consultants to be mindful of seismic measures, local governments can also gradually audit critical public buildings, which are particularly crucial to disaster to response (and may be especially dangerous if they collapse). </p>
<p>Indonesia could even follow California’s example and publicly shame the owners of buildings that the building code. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=358&fit=crop&dpr=1 754w, https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=358&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/231038/original/file-20180808-191044-k4r7b3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=358&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A sign from California alerting passers-by to a potentially dangerous building.</span>
</figcaption>
</figure>
<p>It will require radical reform in public administration, including construction at local level. Without this radical change, the status quo will remain and people will continued to be killed by their houses when moderate to big earthquakes hit their area.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-earthquake-safety-measures-could-have-saved-thousands-of-lives-in-nepal-40907">How earthquake safety measures could have saved thousands of lives in Nepal</a>
</strong>
</em>
</p>
<hr>
<p>The present approach is failing. Stronger political and administrative commitments are needed at all levels.</p><img src="https://counter.theconversation.com/content/101247/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonatan A Lassa recently worked as a DFAT consulant on Disaster Risk Management in Indonesia.</span></em></p>As Indonesia reels from two deadly earthquakes, it’s time to rebuild smarter and stronger.Jonatan A Lassa, Senior Lecturer, Humanitarian Emergency and Disaster Management, College of Indigenous Futures, Arts and Society, Charles Darwin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1006312018-08-01T10:38:21Z2018-08-01T10:38:21ZParts of the Pacific Northwest’s Cascadia fault are more seismically active than others – imaging data suggests why<figure><img src="https://images.theconversation.com/files/229901/original/file-20180730-106514-1rqf4bf.jpg?ixlib=rb-1.1.0&rect=114%2C2%2C1652%2C1092&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What's going on 150 kilometers below the Earth's surface?</span> <span class="attribution"><a class="source" href="https://www.goodfreephotos.com">Good Free Photos</a></span></figcaption></figure><p>The Pacific Northwest is known for many things – its beer, its music, its mythical large-footed creatures. Most people don’t associate it with earthquakes, but they should. It’s home to the <a href="http://discovermagazine.com/2012/extreme-earth/01-big-one-earthquake-could-devastate-pacific-northwest">Cascadia megathrust fault</a> that runs 600 miles from Northern California up to Vancouver Island in Canada, spanning several major metropolitan areas including Seattle and Portland, Oregon.</p>
<p>This geologic fault has been relatively quiet in recent memory. There haven’t been many widely felt quakes along the Cascadia megathrust, certainly nothing that would rival a catastrophic event like the 1989 <a href="https://earthquake.usgs.gov/earthquakes/events/1989lomaprieta/">Loma Prieta earthquake</a> along the active San Andreas in California. That doesn’t mean it will stay quiet, though. Scientists know it has the potential for large earthquakes – as big as <a href="https://www.newyorker.com/magazine/2015/07/20/the-really-big-one">magnitude 9</a>.</p>
<p>Geophysicists have known for over a decade that not all portions of the Cascadia megathrust fault behave the same. The northern and southern sections are much more seismically active than the central section – with frequent small earthquakes and ground deformations that residents don’t often notice. But why do these variations exist and what gives rise to them?</p>
<p><a href="https://scholar.google.com/citations?user=67KN5e4AAAAJ&hl=en&oi=ao">Our</a> <a href="https://scholar.google.com/citations?user=SXGw77gAAAAJ&hl=en&oi=sra">research</a> tries to answer these questions by <a href="https://doi.org/10.1029/2018GL078700">constructing images of what’s happening deep within the Earth</a>, more than 100 kilometers below the fault. We’ve identified regions that are rising up beneath these active sections which we think are leading to the observable differences along the Cascadia fault.</p>
<h2>Cascadia and the ‘Really Big One’</h2>
<p>The Cascadia <a href="https://www.livescience.com/43220-subduction-zone-definition.html">subduction zone</a> is a region where two tectonic plates are colliding. The <a href="https://americastectonics.weebly.com/juan-de-fuca-explorer-and-gorda-plates.html">Juan de Fuca</a>, a small oceanic plate, is being driven under the North American plate, atop which the continental U.S. sits.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229912/original/file-20180731-102467-1oh0x8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Juan de Fuca plate meets the North American plate beneath the Cascadia fault.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Cascadia_earthquake_sources.png">USGS</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Subduction systems – where one tectonic plate slides over another – are capable of producing the world’s largest known earthquakes. A prime example is the <a href="https://www.livescience.com/39110-japan-2011-earthquake-tsunami-facts.html">2011 Tohoku earthquake</a> that rocked Japan.</p>
<p>Cascadia is seismically very quiet compared to other subduction zones – but it’s not completely inactive. Research indicates the fault ruptured in a <a href="https://www.opb.org/news/series/unprepared/jan-26-1700-how-scientists-know-when-the-last-big-earthquake-happened-here/">magnitude 9.0 event in 1700</a>. That’s roughly 30 times more powerful than the largest predicted San Andreas earthquake. Researchers suggest that we are within the roughly <a href="https://projects.oregonlive.com/maps/earthquakes/timeline">300- to 500-year window</a> during which <a href="https://www.newyorker.com/magazine/2015/07/20/the-really-big-one">another large Cascadia event may occur</a>.</p>
<p>Many smaller undamaging and unfelt events take place in northern and southern Cascadia every year. However, in central Cascadia, underlying most of Oregon, there is very little seismicity. Why would the same fault behave differently in different regions? </p>
<p>Over the last decade, scientists have made several additional observations that highlight variations along the fault.</p>
<p>One has to do with <a href="https://www.ldeo.columbia.edu/%7Edjs/aleut/info_for_public.html">plate locking</a>, which tells us where stress is accumulating along the fault. If the tectonic plates are locked – that is, really stuck together and unable to move past each other – stress builds. Eventually that stress can be released rapidly as an earthquake, with the magnitude depending on how large the patch of fault that ruptures is.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=769&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=769&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=769&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=966&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=966&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229900/original/file-20180730-106521-cc0xx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=966&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A GPS geosensor in Washington.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:EarthScope-geosensor.jpg">Bdelisle</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Geologists have recently been able to deploy <a href="https://www.unavco.org/projects/major-projects/pbo/pbo.html">hundreds of GPS</a> monitors across Cascadia to record the subtle ground deformations that result from the plates’ inability to slide past each other. Just like historic seismicity, plate locking is more common in the <a href="http://geodesygina.com/Cascadia.html">northern and southern parts of Cascadia</a>.</p>
<p>Geologists are also now able to observe difficult-to-detect seismic rumblings known as <a href="https://pnsn.org/tremor">tremor</a>. These events occur over the time span of several minutes up to weeks, taking much longer than a typical earthquake. They don’t cause large ground motions even though they can release significant amounts of energy. Researchers <a href="https://doi.org/10.1126/science.1084783">have only discovered</a> <a href="https://doi.org/10.1126/science.1060152">these signals</a> in the <a href="https://doi.org/10.1126/science.1070378">last 15 years</a>, but permanent seismic stations have helped build a robust catalog of events. Tremor, too, seems to be more concentrated along the <a href="https://doi.org/10.1130/G23740A.1">northern and southern parts</a> of the fault. </p>
<p>What would cause this situation, with the area beneath Oregon relatively less active by all these measures? To explain we had to look deep, over 100 kilometers below the surface, into the Earth’s mantle.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=588&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=588&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=588&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=738&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=738&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229896/original/file-20180730-106524-1kc0lc8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=738&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Green dots and blue triangles show locations of seismic monitoring stations.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1029/2018GL078700">Bodmer et al., 2018, Geophysical Research Letters</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Imaging the Earth using distant quakes</h2>
<p>Physicians use electromagnetic waves to “see” internal structures like bones without needing to open up a human patient to view them directly. Geologists <a href="https://www.iris.edu/hq/inclass/animation/seismic_tomography_ct_scan_as_analogy">image the Earth</a> in much the same way. Instead of X-rays, we use seismic energy radiating out from distant magnitude 6.0-plus earthquakes to help us “see” features we physically just can’t get to. This energy travels like sound waves through the structures of the Earth. When rock is hotter or partially molten by even a tiny amount, seismic waves slow down. By measuring the arrival times of seismic waves, we create 3D images showing how fast or slow the seismic waves travel through specific parts of the Earth. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=557&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=557&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=557&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=699&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=699&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229895/original/file-20180730-106499-xy3gha.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=699&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ocean bottom seismometers waiting to be deployed during the Cascadia Inititive.</span>
<span class="attribution"><span class="source">Emilie Hooft</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To see these signals, we need records from seismic monitoring stations. More sensors provide better resolution and a clearer image – but gathering more data can be problematic when half the area you’re interested in is underwater. To address this challenge, we were part of a team of scientists that deployed hundreds of seismometers on the ocean floor off the western U.S. over the span of four years, starting in 2011. This experiment, the <a href="https://cascadia.uoregon.edu/">Cascadia Initiative</a>, was the first ever to cover an entire tectonic plate with instruments at a spacing of roughly 50 kilometers.</p>
<p><a href="https://doi.org/10.1029/2018GL078700">What we found are two anomalous regions</a> beneath the fault where seismic waves travel slower than expected. These anomalies are large, about 150 kilometers in diameter, and show up beneath the northern and southern sections of the fault. Remember, that’s where researchers have already observed increased activity: the seismicity, locking, and tremor. Interestingly, the anomalies are not present beneath the central part of the fault, under Oregon, where we see a decrease in activity.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229899/original/file-20180730-106505-ah3ah8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Regions where seismic waves moved more slowly, on average, are redder, while the areas where they moved more quickly are bluer. The slower anomalous areas 150 km beneath the Earth’s surface corresponded to where the colliding plates are more locked and where tremor is more common.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1029/2018GL078700">Bodmer et al., 2018, Geophysical Research Letters</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>So what exactly are these anomalies?</p>
<p>The tectonic plates float on the Earth’s rocky mantle layer. Where the mantle is slowly rising over millions of years, the rock decompresses. Since it’s at such high temperatures, nearly 1500 degrees Celsius at 100 km depth, it can <a href="https://www.wired.com/2012/12/why-do-rocks-melt-volcano/">melt ever so slightly</a>.</p>
<p>These physical changes cause the anomalous regions to be more buoyant – melted hot rock is less dense than solid cooler rock. It’s this buoyancy that we believe is affecting how the fault above behaves. The hot, partially molten region pushes upwards on what’s above, similar to how a helium balloon might rise up against a sheet draped over it. We believe this increases the forces between the two plates, causing them to be more strongly coupled and thus more fully locked.</p>
<h2>A general prediction for where, but not when</h2>
<p>Our results provide new insights into how this subduction zone, and possibly others, behaves over geologic time frames of millions of years. Unfortunately our results can’t predict when the next large Cascadia megathrust earthquake will occur. This will require more research and dense active monitoring of the subduction zone, both onshore and offshore, using seismic and GPS-like stations to capture short-term phenomena. </p>
<p>Our work does suggest that a large event is more likely to start in either the northern or southern sections of the fault, where the plates are more fully locked, and gives a possible reason for why that may be the case.</p>
<p>It remains important for the public and policymakers to stay informed about the potential risk involved in <a href="https://www.seattletimes.com/seattle-news/science/californias-celeb-quake-expert-says-preventing-damage-is-key-to-quick-recovery/">cohabiting with a subduction zone fault</a> and to support programs such as <a href="https://earthquake.usgs.gov/research/earlywarning/">Earthquake Early Warning</a> that seek to expand our monitoring capabilities and mitigate loss in the event of a large rupture.</p><img src="https://counter.theconversation.com/content/100631/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Doug Toomey receives funding from National Science Foundation and the United States Geological Survey. </span></em></p><p class="fine-print"><em><span>Miles Bodmer does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new array of seismometers provides a glimpse of what’s happening deep beneath this geologic fault. New data help explain why the north and south of the region are more seismically active than the middle.Miles Bodmer, PhD Student in Earth Sciences, University of OregonDoug Toomey, Professor of Earth Sciences, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/958832018-05-31T13:14:12Z2018-05-31T13:14:12ZEvidence suggests fracking linked to South Korea’s 2017 earthquake<figure><img src="https://images.theconversation.com/files/218096/original/file-20180508-34006-e58t6w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="http://www.epa.eu/disasters-photos/earthquake-photos/shelter-for-earthquake-victims-in-pohang-photos-53902019">EPA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>A magnitude 5.5 earthquake shook the industrial city of Pohang in South Korea on 15 November 2017, injuring almost 100 people and damaging thousands of buildings at a cost of millions of US dollars. Six months on, two academic papers have <a href="https://www.theguardian.com/environment/2018/apr/27/fracking-south-korean-earthquake">suggested that fracking</a> was probably the cause of this earthquake.</p>
<p>A local <a href="https://www.renewableenergyworld.com/geothermal-energy/tech.html">geothermal</a> energy <a href="https://doi.org/10.1016/j.proeng.2017.05.250">project</a> had been injecting highly pressurised water into two, four kilometre-deep boreholes for almost two years. This process, known as <a href="https://www.renewableenergyworld.com/articles/print/volume-16/issue-4/geothermal-energy/is-fracking-for-enhanced-geothermal-systems-the-same-as-fracking-for-natural-gas.html">hydraulic fracturing</a> or fracking, creates or enhances fractures in rock to harness the heat stored there.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/AQ9qcb9lTuQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Once the network of fractures connected the two boreholes, the plan was to pump water into one, circulate it through the <a href="https://geology.com/rocks/granite.shtml">granite</a> rock, absorbing heat, then extract it from the other borehole and use the heat to generate electricity. Afterwards, the cooled water would be reinjected to begin the process over again.</p>
<p>The proposed cause-and-effect connections now identified make the Pohang earthquake by far the largest recorded for which fracking is the likely cause. The <a href="https://doi.org/10.1785/gssrl.80.5.784">previous record holder</a> linked to geothermal development – of magnitude 3.4 – occurred a decade ago in the Swiss city of Basel.</p>
<p>Ten days after the Pohang earthquake, the South Korean government suspended the geothermal plant’s operations and ordered an investigation into a possible link, which is still ongoing.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=314&fit=crop&dpr=1 600w, https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=314&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=314&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=394&fit=crop&dpr=1 754w, https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=394&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/218097/original/file-20180508-34027-3yw014.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=394&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The area of Pohang where the 5.5 magnitude earthquake occurred on November 15, 2017.</span>
<span class="attribution"><span class="source">GoogleEarth</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Seismographs, satellites and faults</h2>
<p>The <a href="http://science.sciencemag.org/content/early/2018/04/27/science.aat2010/tab-pdf">first</a> of the papers reports a collaboration between researchers from <a href="https://www.ethz.ch/en.html">Zurich</a>, Switzerland, <a href="https://www.gfz-potsdam.de/en/home/">Potsdam</a>, Germany, and myself. We used public domain data from <a href="https://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Monitoring-Earthquakes/Seismic-Activity/What-are-Seismographs">seismographs</a> (instruments for recording ground motion caused by earthquakes) and remote-sensing <a href="http://www.bgs.ac.uk/research/earthHazards/epom/SatelliteInSAR.html">satellites</a> to determine the location and position of the geological fault that slipped in the earthquake.</p>
<p>Both types of data indicate the rupture of a fault running southwest to northeast and dipping steeply to the northwest. Recorded by satellites, the rock above this fault moved upward, lifting the Earth’s surface by four centimetres. This analysis indicates that the fault slipped over a depth range of three to six kilometres, encompassing the depth of the injection and passing within hundreds of metres of the boreholes. This points strongly to a connection between the high-pressure fluid injection and the earthquake. </p>
<p>The <a href="http://science.sciencemag.org/content/early/2018/04/25/science.aat6081/tab-pdf">second paper</a>, by Korean colleagues, reports the locations of the many <a href="https://earthquake.usgs.gov/learn/animations/aftershocks.php">aftershocks</a> of the Pohang earthquake, more accurately defining its fault plane. As shown in the cross-section below, their study indicates the fault passing between the bases of the two boreholes where water was injected, cutting across one borehole at a depth of around three to four kilometres. The results from the two papers are consistent with each other, despite the different types of data used, providing strong confirmation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/218346/original/file-20180509-184630-1luf3uv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">sciencemag.org</span></span>
</figcaption>
</figure>
<p>Preliminary surveys for the geothermal project over a decade ago <a href="https://www.tandfonline.com/doi/pdf/10.1080/12269328.2003.10541204">identified</a> a fault (its position at a depth of four kilometres is shown in orange on the image below) with essentially the same position and alignment as that which slipped in the November 2017 earthquake (its position, also at a depth of four kilometres, is shown in red for comparison). Taking into account the uncertainties in each of the analyses, this comparison indicates that these surveys revealed the fault that is now known to have slipped in the November 2017 earthquake. </p>
<p>Further surveys taken before drilling started led the developers to revise their <a href="https://www.sciencedirect.com/science/article/pii/S1877705817323901">plans</a> to focus on a WNW-ESE fracture in the granite beneath the site. The boreholes, shown in the cross-section above, were designed for flow in this direction.</p>
<p>During drilling, fluid (or <a href="https://www.rigzone.com/training/insight.asp?insight_id=291&c_id=">drilling “mud”</a>) <a href="https://pangea.stanford.edu/ERE/db/WGC/papers/WGC/2015/06034.pdf">leaked</a> from one borehole at roughly the depth where the fault cuts across the well bore, with <a href="https://earthquake.usgs.gov/learn/glossary/?term=fault%20gouge">fault gouge</a> – crushed rock debris produced by the movement of the rocks on either side of a fault – indicating a fault there before any injection had taken place.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=366&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=366&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=366&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=459&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=459&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217557/original/file-20180503-153869-c7zjsb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=459&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The geothermal project site, north of Pohang, marked in green.</span>
<span class="attribution"><span class="source">Google Earth</span></span>
</figcaption>
</figure>
<h2>Testing the cause-and-effect connection</h2>
<p>More than 20 years ago, a <a href="https://scits.stanford.edu/sites/default/files/207.full_.pdf">set of criteria</a> was devised for assessing whether earthquakes are caused by high pressure fluid injection. The Pohang earthquake meets most of these criteria. Notably, it occurred within hundreds of metres of the injection, and at the same depth. Also, during much of the injection, the pressure was <a href="https://www.sciencedirect.com/science/article/pii/S1877705817323901">high enough</a> for <a href="https://doi.org/10.1029/JB074i022p05343">standard calculations</a> to predict the slipping of the fault, if water at this pressure reached this fault.</p>
<p>However, the two-month interval between the end of injection in September 2017 and the earthquake in November provides a potential argument against any cause-and-effect connection. A possible explanation for this delay is that once water entered the fault it began to dissolve the granite, gradually weakening the fault so it eventually failed and slipped. It seems entirely plausible at this stage to believe that the earthquake was caused by the injection, and to examine the implications.</p>
<p>One reason this seismicity is significant is the disproportion between the size of the main shock and the volume of water injected. A theory has been <a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2013JB010597">developed</a> for determining the “worst case scenario” earthquake feasible for a given volume of fluid injection. The overall volume injected at Pohang was roughly 12,000 cubic metres, whereas this theory requires around 1,000 times more volume to cause an earthquake as large as magnitude 5.5. This suggests that the theory needs improving, possibly to incorporate the injection pressure as well as the injected volume.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217506/original/file-20180503-153884-1svr1vz.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The drilling rig at the Pohang geothermal project site. Work here is now suspended.</span>
<span class="attribution"><span class="source">Rob Westaway</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In the meantime, designs for future geothermal fracking projects might require independent expert assessment, as is already the case for projects involving fracking for shale gas in the UK. At Pohang, this could have highlighted the potential implications of a fault cutting across the site, leading to recommendations such as limiting the injection pressure, which could have lessened the force of the earthquake.</p>
<p>Elsewhere in the world, successful deep geothermal projects have been designed to incorporate circulation of water along faults, requiring high pressure injection to create or enhance fractures. Pohang illustrates the need for accurate information on the geometry of faults on which project designs can be based. </p>
<p>Still, the disproportion between the small volume of water injected at Pohang and the size of the November 2017 earthquake may give geothermal fracking developers worldwide pause for thought. It may well be the game changer for their industry.</p><img src="https://counter.theconversation.com/content/95883/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rob Westaway receives funding from European Commission Horizon 2020 project EC-691728, DESTRESS (DEmonstration of soft Stimulation TREatmentS of geothermal reservoirS).</span></em></p>Two separate studies have concluded that fracking was the likely cause of a fault line rupture, precipitating the 5.5 earthquake.Rob Westaway, Senior Research Fellow, School of Engineering, University of GlasgowLicensed as Creative Commons – attribution, no derivatives.