15 March 2011
From a geological perspective, what is surprising about the Sendai Earthquake?
Posted by Dave Petley
The impact of the Sendai earthquake, and the media coverage of it, is undoubtedly extraordinary. 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. It plays on our fears of the breakdown of society; of catastrophic loss of all we hold dear; and of being trapped. The ongoing nuclear crisis brings back memories of the Cold War, a drum beat to which so many of us grew up. 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. 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.
Against this background it is worth exploring this disaster from the perspective of our knowledge of the Earth system. 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. 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. Surely, from an investment perspective if not one of safety, the true risk of such an event will have been established. Thus, it could be argued that surely the earthquake and tsunami must be a freak or the consequence of something unknown?
Actually, I don’t think so. Indeed, as far as I can see this earthquake, and the resultant tsunami, are remarkably unsurprising. 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. Let’s take the earthquake itself – the existence of the subduction zone to the east of Honshu is well-established. There have been many earthquakes on it in historic times. This is beautifully illustrated in a USGS publication entitled “Seismicity of the Earth 1900—2007, Japan and Vicinity“, which can be downloaded as a PDF. Download it, and send it to every journalist you know. And this is the key part of the map in that publication:
The line of the trench, marking the seabed expression of the junction between the tectonic plates is shown. The red dots are the larger earthquakes. The most interesting aspect is the yellow shaded areas, which show a part of the subduction zone that has undergone a large rupture event. 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. These are areas in which the stored energy can be high, and large earthquakes should be feared.
The Catastrophe Modelling company RMS have produced a map of the area of the fault that is thought to have ruptured, shown below.
Compare the maps – the recent rupture event has efficiently-filled the seismic gap. A rupture event of this size would be expected to generate a very large earthquake. The unruptured section of fault was clear from the USGS map. Thus, there is little of great surprise here.
Second is the shaking itself. Well, the RMS map above shows shaking intensities. MMI intensity of VII onshore a giant subduction zone earthquake is remarkably unsurprising, so nothing out of the ordinary there either.
So how about the tsunami? Well, in 1993 a magnitude M = 7.8 earthquake off Hokkaido generated tsunami waves that were up to 10 metres high. The event is well described in this article (despite the gaudy presentation), which includes this now awfully familiar scene of destruction:
Note that the tsunami broached the protective seawall around the village that was meant to provide a barrier against such events. This case is of course not alone – we know that large subduction zone earthquakes can generate large tsunamis from many historic and recent examples. As a society there is no excuse for our failure to recognise and prepare this.
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. Which of course acts to demonstrate that once again it is our preparedness that is at fault. Once again our knowledge of the hazard has failed to transfer into effective mitigation. This is so deeply frustrating!
Of course there is a crucial need for research into the earth science elements of this issue. 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. It is this failure that probably led to inadequate defence against the tsunami that occurred, with appalling consequences.
Finally, of course, this research needs funding, but (in my – ahem – unbiased opinion) investment in this area is still surprisingly low. 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” (IRNH), which is planned to fund two large projects, one focusing on seismic hazard / risk, and the other on volcanic hazard / risk. Over five years this is expected to receive £7 million funding. 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. These events have cost hundreds of thousands of lives and tens of billions of pounds of losses. Let’s compare this with some other NERC programmes: the Environmental Nanoscience Inititiative is receiving £7.3 million from NERC and the US; the Biodiversity and Ecosystem Service Sustainability programme is receiving £13 million; and the High Resolution Dynamics Limb Sounder received £17 million. 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. I use these figures merely to demonstrate the endemic paucity of investment in research this key area. Without proper investment in our understanding of natural hazards, and in transferring this knowledge to practice, such disasters will continue to occur. The UK Prime Minister, David Cameron, is reported to have said in the aftermath of the earthquake that it was a “terrible reminder of the destructive power of nature”. True, so let’s do something about it!
Comments welcome – maybe you disagree with me? If so, let’s discuss!
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
This is an excellent and thought provoking post thank you. I love that PDF and am currently having a few printed to post around our Natural Science Department. I agree with your statement that “knowledge of the hazard has failed to transfer into effective mitigation”. When you think about it that statement can be applied to many of our natural disasters (Katrina/New Orleans leaps to mind) They rarely really ‘come from nowhere’.
I do wonder though. Is there anyway to adequately prepare for a magnitude 9 earthquake and a tsunami the size of which we’ve seen here? And then also is there a point where preparing for the event becomes so expensive and onerous that people just decide they’d rather live with the danger? I can easily envision a public meeting with people saying they’d rather risk a tsunami every 100 years than have 50 foot wall costing X around their village, and maybe that’s the problem who knows?
High magnitude events like the Sendai earthquake-tsunami are generally beyond what communities can prepare for anywhere in the world. There is indeed a high level of acceptabe risk countries must be willing to accept, in disaster prone areas, either at the onset or after some deliberation. Inevitably, disaster prepardness is limited to certain magnitude events, or course, constrained by GDP/GNP. Beyond a certain size, maybe 7.5 and above, one has to accept significant loss, even in the most developed countries where state of the art engineering exists. This was noted in Kobe, the Northridge event, and the recent Chile event
Dear Dave,
Thanks for the comments and narrative above.
What is really interesting here is, are we as a global community, where natural hazards abound, prepared for such disasters? How much are megacities will to tolerate along coastal fringes, in high risk areas? What is acceptable loss? Japan, like many other hazard prone countries in the Pacific Rim know the high risk, even if other countries many not be equally disposed. While structural design is now elaborate and sophiscated, there is only so much civil engineering that is possible in a tectonically unstable area, where earthquakes by the 1000’s are experienced daily. There are lessons one should learn from the Kobe 1995 event, the Northridge earthquake, the Chile event, and similar events like in the New Madrid Fault Zone. However, what are we using these forensic analysis for, if megacities and critical facilities are still being constructed in hazard prone areas.
To boot there was an earthquake an tsunami in 869 AD that appears to be very similar. Here is a link to one post that suggests that event could have been a 9.0 also:
http://www.tsunami-alarm-system.com/fileadmin/media/press/articel/en/Daily-Yomiuri-12_10_2007-Was-869-Tohoku-quake-Japans-strongest.pdf.
The work was done by looking at runup deposits of the tsunami, it appears that there was a volcanic event a decade or so later that put down a nice ash layer to date things. The consensus appears to be that the event was an 8.6 but back guesstimating the size of an event from tsunami runup is at best an extremly inexact game. If the author is of the post is right then this event was even more predicitable. In fact the article suggest that in the last 2500 years there have been 3 such events before this one.
As Paul suggests its hard to justify preparing for an event that might occur in your lifetime or maybe in 40 generations or more. (The NPV for an event 40 generations from now is vanishingly small for any reasonable discount rate) Its like the question of how much would you spend to prevent an event in 3000 ad?
Thanks to both Lyle and Paul for these comments, which are very interesting and helpful. Three things to note. First, a spacing between events of 1000 years does not mean that the return period of the event is 1000 years. A much bigger catalogue is needed to ascertain this. Second, historic records suggest that this area will have suffered other tsunami events in the intervening time, even if there are no deposits to mark them. And third, as a society we really need to sort out how we understand and manage the risk associated with rare events with catastrophic consequences.
Agreed that happening once every thousand years is a lot like the 100 year flood which says the chance is about 1% for the flood in a given year. The 1000 year period would put a .1% chance of it happening in any given year in the absence of a record longer than human history. Reallistically for example the only reason we know the date of the 1700 cascadia event is because it caused a tsunami in Japan.
But risk reward ends up being an version of cost benefit analysis and one needs to at least have a guess at the risk to figure out what a theoretical insurance premium might be.
Hi Dave, you’re quite right, but what you say happens also in Italy, where i live. I work in high Tuscany e in the last two years we have had many problems with natural disaster occurred from strong storms. No money and so no works done. Local political don’t understand the importance of prevention for two reasons: first for ignorance and misunderstanding; second because is better spent money in feast or “light bulbs”. The prevention from natural disaster in Italy is unknown.
Paolo
Dave: Thanks as always for thought-provoking and informative posts. The pdf in particular is something I will now incorporate into my communications with media and also information lectures at the university. There are a lot of questions now (particularly by journalists) whether the sea walls that were put into place were appropriate for a ‘typical’ large tsunami. One, I thought, thoughtful article is here: http://www.nytimes.com/2011/03/14/world/asia/14seawalls.html discussing the sea walls, and how the strategy of building them will now change (and potentially work on changing the false sense of security they gives people). The issues about the research funding is well taken. The whole issue of uncertainties and natural hazards is of keen interest (and importance) to many in my immediate circles, with some funding there, but not many, as you mention, directed calls. But of course many of us that work in that area of research, always want ‘more’ money for our own research.
I suspect a wall would need to be considerably higher than 15 m to stop a 15 m tsunami. The existing walls in Japan may do good in minor cases, but they are already extremely costly and as we have sadly seen completely ineffective when a big one hits.
Today’s paper carries a story that a number of municipal shelters failed at considerable cost of life. We do see that modern structures with solid foundations allowed survival on upper stories — credit to the designers and building codes.
Warning time in this zone is particularly problematic. Worthy of consideration would be well anchored watertight concrete shelters in residences and smaller businesses establishments — perhaps along with a supply of tools to allow those inside to dig out through any debris.
The structures seemed to come through the earthquake just fine; so, we’ve got a demo of good building codes.
The high, concrete structures came through the tsunami as well. Perhaps any coastal construction should be in high, concrete structures. The first 3 floors being non-essential, pass-through enterprises like car parks, storage, gymnasiums, etc. The next few floors would be business and retail. Residences would be above this.
Just a thought
[…] avuto sulla terraferma e, quindi, anche nella zona della centrale nucleare danneggiata. Nel blog di Petley ho trovato la prima risposta; una carta dell’intensità misurata nella scala Mercalli […]
This is a good post, and I agree to some parts. Knowledge is good, but once we have the knowledge, how should we handle it? If prediction can be so accurate that it is possible to say when an earthquake or tsunami will come and of what size, then it is easy. But if the result is a probability then it is necessary to weigh in other factors.
All solutions will have limitations and the chosen solution is a balance between cost and benefit. Apart from cost as money and benefit as a statistical risk reduction, there is also the alternative use of resources (money). That varies between countries of a number of reasons, but it may not be rational to construct anti tsunami walls to avoid a ten year or hundred year event if there is large social needs, or if the people prefer an undisturbed sea view.
In the end it comes down to values and conflicting needs. Although frustrating, the choice of not taking precautionary measures may be the correct choice. But then the facts must right, and that is another problem – there will always be limits in our knowledge.
I am in agreement. Living in Washington State on the Cascadia subduction zone I find the lack of regard for the risk in planning and development in our sttae frustrating. David Cameron’s quote “a terrible reminder of the the power of nature” should be tuned to “a terrible reminder of the coast of ignoring an obvious risk.”
As always, thanks for the great write up.
I agree, the problem is that risk does not translate into actions, however which actions should Japan have taken? There are walls against tsunami, building codes against the effects of ground shaking. Shelters and a well prepared army of helpers. The population knew of the risk and reacted accordingly mostly seeking higher ground or stable structures.
The only foolhardiness I can see is building 6 reactors on the shoreline in a seismic zone prone to destructive tsunami and massive earthquakes. This could and really should have been avoided.
Funding science is a great idea, BUT
money needs to be spent in fortifying buildings so that they don’t fall during a large-magnitude EQ. Dan brings up the Cascadia zone — I just read that school buildings in Oregon may stand long enough to evacuate children, but they won’t survive even an M=6 earthquake. Shouldn’t the gov’t be spending more money on making sure people don’t die during these events? Maybe you can explain how more money in basic research (other than early-warning systems, which Japan already does *very* well) will save cost down the road.
The geophysicist Joachim Saul from the GFZ German Research Centre for Geosciences (Helmholtz Association) created an animation which shows the sequence of quakes since March 9.
http://aqviva.dk/2011/03/animation-japan-earthquake-disaster/
Rise of the sea floor of up to 7 meters was the cause of the tsunami
http://aqviva.dk/2011/03/rise-of-the-sea-floor-of-up-to-7-meters-was-the-cause-of-the-tsunami/
Hi dave, i’have written the article: Voglio una Vera informazione”, that means “i want a true information”, refer to the situation in Italy according to media. Infatc,also famous italian geologist, the day after the quake said this was 30.000 more powerful than Abruzzo (Italy) 2009. This is true if you correlate the Mw of Japan (8.9) with Abruzzo (6.2), but there is a great difference: the first was in the sea at a distance more than 150 km from Fukushima, and the second was 10 km from the city of l’Aquila. In this case the sismic intensity to Fukuschima (VII MMI) is less than L’Aquila (VII-IX Mercalli). I’have made this reasonig uncountable thanks to your blog information from RMS and also aidded from JMA. I suppose there are different from the real situation and the italian media about powerfull of earthquake. Do you think i got a good process data? Bye. Paolo
[…] Dave Petley argues at The Landslide Blog, the Tohuku earthquake is entirely consistent with our understanding of how subduction zones work. However, the size of this particular earthquake does seem to have been a little beyond what was […]
Cascadia has had repeated great subduction earthquakes with subsidence Geological Society of America Bulletin November/December 2010 has a very good article Rupture area and displacement of past Cascadia great earthquakes from coastal cosiesmic subsidence by Leonard, Currie, Mazzotti, and Hyndman. Interseismic uplift is followed by coseismic subsidence, resulting in layers of paleosoils buried beneath marsh mud. This indicates the danger of human activities such as building on the uplifting areas, because they will subside with the tsunami wiping out the vanities of human existence. People don’t know any better and are fooled by real estate developers into believing everything is safe in their waterfront homes. Environmentalists have worked to prevent this human encroachment by making public land out of marsh and low lying areas to protect habitat. Although tsunamis turbulent high energy rips over subsiding habitat, habitat it sure is a good excuse to create public land in such low lying areas vulnerable to subsidence with tsunami which also endanger property values, the economy, and human lives. Better to create protective “tsunami parks” than be responsible for the human cost when it happens.
In response to the Tohoku Earthquake and Tsunami Mar 11th 2011, the Harvard Center for Geographic Analysis has launched a web portal including a lot of geological data.
http://aqviva.dk/2011/03/harvard-center-for-geographic-analysis/
Please find a selection of geological responses and tools on the Japan Quake and Pacific tsunami here:
http://aqviva.dk/tags/tohoku/
I saw a clip on CNN or Fox (forgot which) probably taken from a ship where the tsunami would be felt as a swell. The tsunami was seen, in a characteristic tsunami wave shape going along until it ran over the nuclear power plant with an explosive eruption of steam. It looked like a science fiction horror movie, but for real and human workers were there. To make a realistic horror movie set, build a nuclear power plant to low, just where the worst case scenario tsunami will go. Japan had enough of those in the past, and there was no excuse for building it there. This is clearly caused by stupidity in planning. Only the most necessary structures that need to be along the water, such as shipping docks and fishing docks should be built where tsunami could periodically wipe them out, not industrial buildings, power plants, commercial businesses, and dwellings. Tsunami zone planning should concentrate on making parks and wildlife refuges with temporary human visitation. That prevents the catastrophic loss of life, property and also the environmental pollution with trash floating in the water. It is natural for a tsunami to run through a wildlife refuge leaving a swath of organic debris, but like a science fiction horror movie become real when it runs over a nuclear power plant. Please, wherever you see planning in a tsunami zone that looks like the set for a future horror movie, get on the case of whoever is planning that.
Cleo Paskal, Associate Fellow, Royal Institute of International Affairs, has recently written on how risk assessment can be ‘legally’ bypassed and evaded in: Why We Build Nuclear Power Stations in Earthquake Zones, Huffington Post, 20 March .
For a straightforward example of fraud relating to a New Delhi building, in today’s Hindustan Times of New Delhi, where a contractor allegedly “used computer generated forged earthquake proof certificate, bill and other documentation to shield the poor construction of the building”: . An article concerning the same affair from Outlook, New Delhi, dated 23 November 2010: .
The first posting deleted the links, this is a second try:
Cleo Paskal, Associate Fellow, Royal Institute of International Affairs, has recently written on how risk assessment can be ‘legally’ bypassed and evaded in: Why We Build Nuclear Power Stations in Earthquake Zones, Huffington Post, 20 March http://www.huffingtonpost.com/cleo-paskal/why-we-build-nuclear-powe_b_838062.html
For a straightforward example of fraud relating to a New Delhi building, in today’s Hindustan Times of New Delhi, where a contractor allegedly “used computer generated forged earthquake proof certificate, bill and other documentation to shield the poor construction of the building”: http://www.hindustantimes.com/Delhi-Police-crack-builder-architecture-firm-nexus/Article1-678778.aspx An article concerning the same affair from Outlook, New Delhi, dated 23 November 2010: http://news.outlookindia.com/item.aspx?702283
read :
The 869 Jogan tsunami deposit and recurrence interval of large scale tsunami on the Pacific coast of northeast Japan, by K. Minoura,
http://www.jstage.jst.go.jp/browse/jnds/23/2/_contents