{"id":2730,"date":"2011-03-15T21:10:51","date_gmt":"2011-03-15T21:10:51","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=2730"},"modified":"2011-03-15T21:10:51","modified_gmt":"2011-03-15T21:10:51","slug":"from-a-geological-perspective-what-is-surprising-about-the-sendai-earthquake","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2011\/03\/15\/from-a-geological-perspective-what-is-surprising-about-the-sendai-earthquake\/","title":{"rendered":"From a geological perspective, what is surprising about the Sendai Earthquake?"},"content":{"rendered":"

The impact of the Sendai earthquake, and the media coverage of it, is undoubtedly extraordinary.\u00a0 This is a tragedy that has so many dimensions, ranging from tragedy (in so many cases) to ecstasy (as a survivor is found), including farce and the surreal.\u00a0 It plays on our fears of the breakdown of society; of catastrophic loss of all we hold dear; and of being trapped.\u00a0 The ongoing nuclear crisis brings back memories of the Cold War, a drum beat to which so many of us grew up.\u00a0 And the effects of the disaster continue to ripple outwards, and will do so for years to come, as the financial markets, insurance industry and energy generators strive to face the consequences.\u00a0 Of course for most of us life will go on essentially as before, but in every case at least some, often intangible, elements will have changed.<\/p>\n

Against this background it is worth exploring this disaster from the perspective of our knowledge of the Earth system.\u00a0 It would be reasonable to surmise that such a catastrophic disaster in one of the best-prepared nations must have involved some unknown or unexpected element; some facet of earthquakes or tsunamis of which we were not aware.\u00a0 This is surely doubly the case with the nuclear reactors – these systems each cost literally billions of pounds to build, and pumping sea water into them in a desperate attempt to stabilise the temperatures is enough to ruin them forever, leaving someone with a huge bill to pay.\u00a0 Surely, from an investment perspective if not one of safety, the true risk of such an event will have been established.\u00a0 Thus, it could be argued that surely the earthquake and tsunami must be a freak or the consequence of something unknown?<\/p>\n

Actually, I don’t think so.\u00a0 Indeed, as far as I can see this earthquake, and the resultant tsunami, are remarkably unsurprising.\u00a0 They are exceptionally large for sure, and they were not predictable, but they are not beyond the bound of human experience in any way that I can see.\u00a0 Let’s take the earthquake itself – the existence of the subduction zone to the east of Honshu is well-established.\u00a0 There have been many earthquakes on it in historic times.\u00a0 This is beautifully illustrated in a USGS publication entitled “Seismicity of the Earth 1900\u20142007, Japan and Vicinity<\/a>“, which can be downloaded as a PDF<\/a>.\u00a0 Download it, and send it to every journalist you know.\u00a0 And this is the key part of the map in that publication:<\/p>\n

\"\"<\/a><\/p>\n

The line of the trench, marking the seabed expression of the junction between the tectonic plates is shown.\u00a0 The red dots are the larger earthquakes.\u00a0 The most interesting aspect is the yellow shaded areas, which show a part of the subduction zone that has undergone a large rupture event.\u00a0 Note the lack of stippled area to the south – i.e. this was an area that had not undergone a large rupture event in the last century – a so-called seismic gap.\u00a0 These are areas in which the stored energy can be high, and large earthquakes should be feared.<\/p>\n

The Catastrophe Modelling company RMS have produced a map of the area of the fault that is thought to have ruptured<\/a>, shown below.<\/p>\n

\"\"<\/a><\/p>\n

Compare the maps – the recent rupture event has efficiently-filled the seismic gap.\u00a0 A rupture event of this size would be expected to generate a very large earthquake.\u00a0 The unruptured section of fault was clear from the USGS map.\u00a0 Thus, there is little of great surprise here.<\/p>\n

Second is the shaking itself.\u00a0 Well, the RMS map above shows shaking intensities.\u00a0 MMI intensity of VII onshore a giant subduction zone earthquake is remarkably unsurprising, so nothing out of the ordinary there either.<\/p>\n

So how about the tsunami?\u00a0 Well, in 1993 a magnitude M = 7.8 earthquake off Hokkaido generated tsunami waves that were up to 10 metres high.\u00a0 The event is well described in this article<\/a> (despite the gaudy presentation), which includes this now awfully familiar scene of destruction:<\/p>\n

\"\"<\/a><\/p>\n

Note that the tsunami broached the protective seawall around the village that was meant to provide a barrier against such events.\u00a0 This case is of course not alone – we know that large subduction zone earthquakes can generate large tsunamis from many historic and recent examples.\u00a0 As a society there is no excuse for our failure to recognise and prepare this.<\/p>\n

So, actually, as far as I can see from a geological perspective there is nothing terribly surprising about this earthquake in terms of location, timing, magnitude or secondary hazards.\u00a0 Which of course acts to demonstrate that once again it is our preparedness that is at fault.\u00a0 Once again our knowledge of the hazard has failed to transfer into effective mitigation.\u00a0 This is so deeply frustrating!<\/p>\n

Of course there is a crucial need for research into the earth science elements of this issue.\u00a0 In particular, the ongoing crisis in the nuclear facilities demonstrates that our ability to actually understand magnitude – frequency relationships for large, rare events is tragically weak.\u00a0 It is this failure that probably led to inadequate defence against the tsunami that occurred, with appalling consequences.<\/p>\n

Finally, of course, this research needs funding, but (in my – ahem – unbiased opinion) investment in this area is still surprisingly low.\u00a0 For example, in the UK two research councils (NERC and ESRC) are just embarking on a joint 5 year research programme entitled “Increasing Resilience to Natural Hazards<\/a>” (IRNH), which is planned to fund two large projects, one focusing on seismic hazard \/ risk, and the other on volcanic hazard \/ risk. \u00a0\u00a0 Over five years this is expected to receive \u00a37 million funding.\u00a0 Now this is certainly not a trivial amount, but in the last 15 months we have seen the Haiti earthquake, the Icelandic volcano, the Chile earthquake, the Christchurch earthquake and now the Sendai earthquake.\u00a0 These events have cost hundreds of thousands of lives and tens of billions of pounds of losses.\u00a0 Let’s compare this with some other NERC programmes: the Environmental Nanoscience Inititiative is receiving \u00a37.3 million from NERC and the US; the Biodiversity and Ecosystem Service Sustainability programme is receiving \u00a313 million; and the High Resolution Dynamics Limb Sounder received \u00a317 million.\u00a0 This is not to criticise the IRNH team in any way – they have done a great job in putting this together – or indeed NERC itself, which faces multiple conflicting pressures that are impossible to resolve, and will of course argue that great research can always apply for funding through the responsive (blue skies) route.\u00a0 I use these figures merely to demonstrate the endemic paucity of investment in research this key area.\u00a0 Without proper investment in our understanding of natural hazards, and in transferring this knowledge to practice, such disasters will continue to occur.\u00a0 The UK Prime Minister, David Cameron, is reported to have said in the aftermath of the earthquake that it was a \u201cterrible reminder of the destructive power of nature\u201d.\u00a0 True, so let’s do something about it!<\/p>\n

Comments welcome – maybe you disagree with me?\u00a0 If so, let’s discuss!<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

This post explores whether Friday’s magnitude 9 earthquake in offshore Sendai in Japan was a surprising event from a geological perspective, concluding that there are few aspects of this event that have not been observed elsewhere before.<\/p>\n","protected":false},"author":22,"featured_media":2731,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[23,469,361,128],"class_list":["post-2730","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-earthquake","tag-featured","tag-japan","tag-tsunami"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/2730","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=2730"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/2730\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/2731"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=2730"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=2730"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=2730"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}