Feel free to use these quotes in your stories. Any further comments will be posted here. f you would like to speak to an expert, please don’t hesitate to contact us on (08) 7120 8666 or by email.

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Kevin McCue is an adjunct professor at CQUniversity, President of the Australian Earthquake Engineering Society and Director of the Australian Seismological Centre.

“According to the USGS website the magnitude 8.7 earthquake occurred well offshore, at least 300 km west of Sumatra so the damage onshore on Sumatra is likely to be minimal. The magnitude may well be decrease to 8.5 or 8.4 after more analysis. The epicentre is well west of the plate boundary and in the Indian Ocean, a fracture along the hinge where the subducting slab of oceanic crust starts bending downward and under Sumatra.

The mechanism seems to have been predominantly strike-slip ie no substantial vertical displacement of the sea floor so any tsunami would be small and local.”

———–

Professor James Goff is Director of the Australia-Pacific Tsunami Research Centre and Natural Hazards Research Laboratory, University of New South Wales.Note that Professor Goff is currently in the Cook Islands and so has limited availability for interviews.

“Like everyone else who just heard this news, we are now waiting to see what comes to pass. BUT, the tsunami warning system has worked well, and a tsunami watch is in place. Many people have self-evacuated and fortunately, because of the incredible amount of tsunami-related work in the region, since the massive 2004 event authorities and the general public are considerably better prepared this time. Those of us who are not in the region at the moment will now be monitoring developments over the next few hours.

It appears to be a strike-slip fault which means that it is unlikely to generate a large tsunami, but then we hear that at least small ones have been reported. Of course such a large shake could generate submarine landslides (like in Haiti) which can also generate tsunamis. We continue to watch.”

———–

Professor Kevin Furlong from Pennsylvania State University is currently in the US and is working with the US Geological Survey on this disaster. He is available for interview over the next 8 hours.

“The 11 April 2012, Mw 8.7 earthquake west of Banda Aceh, Sumatra, Indonesia is a very large earthquake within the Indo-Australian plate. Although it is within the plate, its occurrence is almost certainly linked to the plate interactions between Indo-Australian plate and Indonesia (part of the Sunda segment of the Eurasian plate).

This earthquake reflects a style of faulting (strike-slip) which involves principally horizontal motion, and thus is unlikely to generate a significant tsunami; although very strong ground shaking would be felt on Sumatra. This is also an extremely large magnitude earthquake for this style of faulting, meaning that it likely involved substantial fault movement, and the fault likely extends for 200+ km This earthquake is of the same style of faulting and in approximately the same location as a Mw 7.2 earthquake on January 10, 2012.

Although this earthquake was within the Indo-Australian plate, any earthquake of this size will change the stress regimes acting on the nearby plate boundaries. The result is that stress conditions on the subduction plate boundary beneath Sumatra have changed, although the implications of that change are uncertain.”

———–

Associate Prof Huilin Xing is Deputy Director of the Earth Systems Science Computational Centre (ESSCC) at the University of Queensland’s School of Earth Sciences.

“This earthquake (M8.6) and following major aftershock M8.2 may be located at a splitting boundary that indicates the Indo-Australian Plate is splitting into two plates – the Indian plate and Australian plate.

If so, the mechanism would be different from the previous major Sumatra subduction earthquakes such as M9.1 in 2004 and thus a tsunami generated by the current earthquakes (M8.6 and M8.2) should not be that severe.”

Additional comment:

“The tsunami warning system worked again but not that perfect as expected. It’s better than nothing … But the problem is that there were a lot of false alarms, because not all large earthquakes can generate a tsunami. From research we know we can expect that if an earthquake is larger than magnitude 6.5 there may be a tsunami, but this is not directly or linearly related to size. This means we really need to keep looking deeper to work out what kinds of earthquakes can generate tsunamis and how big the tsunami might be. This is the most difficult part since one needs to know details of both the earthquake itself (i.e. depth and focal mechanism) and its triggered sea floor motion and interaction with water. Currently no single model can model the whole process of an earthquake and its triggered tsunami. It does needs a lot of research to do. It may take years before tsunami warnings can be made accurate enough to avoid such unnecessary evacuations or alerts, but it does depend also on the investment in it.”
———–

Comments from UK experts (collated by our colleagues at the UK Science Media Centre):

Dr Andy Gibson, Director of the Centre for Applied Geoscience at the University of Portsmouth, said:

“From our experience of the tsunami in 2004, we know that the worst affected regions are those low lying areas immediately adjacent to the coast. Broadly speaking, the shallower the slope of the shore, the greater the susceptibility to wave run-up. Areas farther inland could be affected if the tsunami was able to move along a water inlet. Lessons learned from that tsunami go far beyond early warning systems, residents are encouraged to take part in emergency drills which may include understanding escape routes, identifying safe havens and knowing when it is safe to return to the coast.

“Early indications are that this earthquake and tsunami risk are actually much smaller than that of 2004, but it will be some time before the pattern of any damage is known. It is always difficult to estimate damage as any tsunami wave depends upon many factors such as the volume of water displaced, the angle it approaches the coast, tidal conditions, the gradient of land offshore and onshore and of course, what is found on the shoreline.”

———–

Dr Susanne Sargeant, Seismologist & NERC Knowledge Exchange Fellow, British Geological Survey, said:

“Critical information that is required to assess the potential for a tsunami is the location, magnitude, depth and faulting mechanism. Tsunamis are caused when vertical displacement of the seafloor occurs. In the case of the 11 April earthquake, an earthquake of this magnitude (8.7 Mw) has the potential to generate an ocean-wide tsunami. However, although the earthquake is relatively shallow and offshore, the data indicate that the earthquake was the result of movement on a strike-slip fault. Strike slip earthquakes are caused when two blocks move horizontally past each other. Such an earthquake would not lead to the vertical displacement of the sea floor that would be required to generate a tsunami. Consequently, the potential for a large tsunami from this earthquake is likely to be low.

“The alert from the Pacific Tsunami Warning Centre issued after the earthquake indicates that an Indian Ocean wide tsunami watch is in place. See http://ptwc.weather.gov/ptwc/text.php?id=indian.TSUIOX.2012.04.11.1054 for info. Arrival time estimates issued by PTWC indicate that the initial wave (had one been generated) would have reached Banda Aceh a little under an hour after the earthquake. Whether any wave has been observed in this region has yet to be confirmed. The PTWC alert gives estimated arrival times for other locations in the Indian Ocean.

“The Sunda trench region is highly active. Earthquakes here are related to subduction of the Indian plate beneath Eurasia. Today’s earthquake occurred on a structure related to the subduction that is occurring here. The tectonics of the region are complex and large earthquakes are relatively frequent. The aftershock sequence has started and this includes an earthquake of magnitude 8.3.

“Although large, the 08:38 UTC earthquake is located approximately 400 km from the coast of Banda Aceh. As such, the potential for significant damage caused by ground shaking is likely to be relatively low although the actual impact of the earthquake in this region has yet to be confirmed.”

———–

Q&A ON AFTERSHOCKS Dr Bruce D. Malamud, Reader of Natural and Environmental Hazards, Department of Geography, King’s College London:

How many and what size aftershocks might we expect?

“When an earthquake occurs, it releases stress that has built up over time, along a fault. However, in addition to releasing stress, it redistributes the stress along that fault, and sometimes these will be redistributed to other nearby faults. In the case of the 11 April 2012 earthquake that occurred off the west coast of Northern Sumatra, the preliminary estimate of magnitude by the USGS is M8.6, and hundreds of km of fault may have been affected. With the redistribution of stress, aftershocks occur, for weeks, to months (and sometimes years) after the main shock. The magnitude 8.6 earthquake will result in aftershocks occurring all along the fault on which the original earthquake occurred. Some scientists say that one can expect aftershocks as much as 1 unit less than the original shock. So in this case, we might expect aftershocks of all sizes, but as big as a magnitude of about 7.6 (which would be in itself a concern of potentially triggering a tsunami).

How long might aftershocks continue for?

“After an earthquake occurs along a fault, stress is released in parts. But then, part of this stress is redistributed to other parts of the fault. This means that they are now more likely to become unstable, with many subsequent earthquakes. Aftershocks can continue for weeks and months after the main shock (the biggest earthquake in the sequence), sometimes even years.

How frequent have earthquakes been over the last century and are they increasing?

“One of the questions that has been asked by many is whether there have been more frequent large earthquakes in the last few years. Let’s take as a ‘large’ earthquake one with moment magnitude 7. The number of earthquakes per year with moment magnitude greater than or equal to 7 varies certainly, year to year, but the average from 1900 to present is about 17 magnitude 7 or greater earthquakes per year (compared to about 1 magnitude 8 or greater earthquake). If we just look at 1990 to 2010, then the average was about 15 magnitude 7 or greater earthquakes per year. And if we look at the last three years, then the average is also 15 of this size earthquake per year. So, no, the actual number of very large earthquakes is not increasing over time. It fluctuates year to year, with some years less and some years more.

How much energy is released in a magnitude 7 earthquake?

“Equivalent to the energy released in half a megaton nuclear bomb.

How much energy is released in a magnitude 9 earthquake?

“Equivalent to 1000 times the energy released in a magnitude 7 earthquake, or one thousand half-megaton nuclear bombs. If we converted this to energy, this would be roughly enough to power every home in the USA for 50 days.

How accurately can an earthquake like this be predicted? Why is it so difficult to predict the timing of earthquakes?

“For a complete prediction, we need to tell people when a disaster will occur, where, and how big. As scientists, we have a good idea of where large events might occur based on written and instrumental records of past events. So for instance, we know that Indonesia is near subduction zones, and that there is an extensive history of earthquakes in the past, so we know that Indonesia is likely to experience earthquakes. Based on these past records, we can also forecast the chance that a given size or larger earthquake might occur, in a given year. This is called probabilistic hazard forecasting, and has been very useful in telling us about how big we might expect, on average, each year. But true prediction is much more difficult, where we tell people that ‘next week there will be an earthquake of magnitude of 9’. Although scientists have been trying for many years to predict earthquakes (the when and how big), they so far have not succeeded, but are still working at it.”

———–

Dr David Rothery runs the Open University’s Volcanoes, Earthquakes and Tsunamis course in the UK

“Today’s M8.7 quake in the Indian Ocean offshore of Sumatra has the potential to cause a tsunami that could cause devastation to coasts all around the Indian ocean. A tsunami warning from the Pacific Tsunami Warning Centre predicts tsunami wave arrival at Banda Aceh (Sumatra) 10:31 BST, and Sri Lanka between 11.30 and 12.30 BST.
http://ptwc.weather.gov/ptwc/text.php?id=indian.TSUIOX.2012.04.11.0845

A tsunami detection buoy (a DART station) in the Bay of Bengal http://www.ndbc.noaa.gov/station_page.php?station=23227
detected a wave with an amplitude of 30 cm in deep water (see figs below), which has the potential to become several times higher as it approaches the shore.

Today’s quake was probably about ten times less energetic than the M9.1 quake that caused the 26 Dec 2004 Indian Ocean tsunami. In addition, the nature of the quake, on the bending Indian ocean floor as it approaches the Sunda Trench (rather than a megathrust quake in the trench itself) may mean that the displacement of water to trigger the tsunami is less bad; the motion of the sea bed is different to that which occurred in 2004.”

———–

Comments from Canadian experts (collated by our colleagues at the Canadian Science Media Centre):

Tad Murty is Adjunct Professor in the Department of Civil Engineering, University of Ottawa

“My career was mostly with the federal government. When I was with the government, I was in charge of research and programming of tsunami early warning systems. I was involved in developing computer programs for the Canadian early warning system. The system is similar in Canada, Indonesia, India, everywhere, because the same principles apply.

If there is a large earthquake far from the ocean, on land, there is no tsunami. The earthquake itself needs to be shallow – some 20 or 30 km below the ocean bottom before it can generate a tsunami, and it needs to be a dip slip, like a subduction. The movement needs to be vertical, not horizontal. In today’s earthquake in Indonesia, the movement was horizontal, because the Indian plate slid past the Burmese plate.

In 2004, the Indian Plate went under the Burmese plate, and tens of cubic kilometres of water were suddenly displaced and piled at the ocean surface. This is what causes a tsunami.

How do early warning systems work?

There are many different kinds of detectors, and one can never depend on just one set of detectors. First, the earthquake itself has to be detected. This is done by seismographs, and these are mostly on land. Earthquake waves propagate through the interior of Earth’s crust, as well as earth’s surface.

We also have ocean-bottom pressure sensors. There are several dozen all around the ocean. They are the first indicators of a tsunami. Then we have tidal gauges, on land but on the coast, put in the water, and they catch the tsunami coming in. By then it’s usually too late.

Indonesia has an early warning system. But all the international agencies work together. They are all part of the Intergovernmental Oceanographic Commission, and that’s all coordinated by UNESCO.

Have there been any changes in the tsunami warning system since 2004?

Following the disaster in 2004, the first early warning systems were placed in the Indian Ocean.

With each disaster we learn new things. On the scientific side, we already know the physical principles but we fine-tune our computer models and we make our instruments more precise. The physical process is the same. On the social and economic side, there has been progress, for example, with evacuations.

When a cyclone hits in the area, almost all the damage and loss of life comes from the storm surge. In developing countries like India and Bangladesh, they use a ‘vertical evacuation system’. Because you can’t evacuate millions of people from the area, the infrastructure and the roads just aren’t there. So they built cyclone shelters on the coast, that are well built and can withstand storm surges and cyclones. In the US, they use a ‘horizontal evacuation system’, because the highways are good and the roads are there so people just move away from the coast.

In the 2004 tsunami, none of the cyclone shelters in India were damaged. So they thought maybe they could use them for tsunamis as well. Now, if there has to be an evacuation for a tsunami, they use the cyclone shelters.”

On March 11 last year a magnitude 9.0 (Mw) earthquake hit off the coast of Japan triggering a powerful tsunami and resulting in the most serious nuclear accident since Chernobyl. Over 15,000 people were confirmed dead as the tsunami inundated a total area of approximately 561 km2 (217 sq mi) in Japan. A series of fires and explosions within the Fukushima Daiichi nuclear power station triggered a full meltdown in three reactors whilst a fourth was significantly damaged by fire. The Fukushima Daiichi nuclear disaster was rated as a level 7 (major accident) on the international nuclear and radiological event scale. Now, one year after the disastrous events unfolded, nuclear and disaster experts examine the current situation and what lessons can be learnt.

Below are comments from Japanese experts gathered by our friends at the Science Media Centre of Japan and translated into English by Translationz. The collaboration between the Australian Science Media and the Science Media Centre of Japan is supported by the Commonwealth through the Australia-Japan Foundation which is part of the Department of Foreign Affairs and Trade.

To see comments from Australian, UK and Canadian experts, click here.

Feel free to use these quotes in your stories.  Any further comments will be posted here. If you would like to speak to an expert, please don’t hesitate to contact us on (08) 7120 8666 or by email.

AusSMC hosted an online briefing on this issue on Tuesday 6 March with Japanese, UK and Australian experts – a full copy of the briefing is available here: http://www.aussmc.org/2012/03/background-briefing-fukushima-one-year-on/

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Tatsujiro Suzuki is Vice-Chairman of the Atomic Energy Commission in the Japanese Cabinet office

“The present circumstances assure that Fukushima Daiichi is remarkably stable. However, the condition of the reactor core is not understood and there are still many mysteries about the nuclear reactor.

At present the main concern is the radioactive material being discharged in large quantities into the air. However, I think that this is a short-term concern. I feel as a future prospect, the treatment of contaminated water being generated in large quantities would be more important. The water is being processed; it however is not decreasing. The people at Fukushima Nuclear Power Plant are suffering a lot due to this. The influx has already entered the sea. Effort is being made to build a fence, however this would take time. Groundwater is flowing under the power plant; hence one has to keep watch on underground penetration. In the case of the contaminated water, a liquid waste disposal process has to be set up as it is a high level radioactive waste.

Robots started operating at the power plant a few days ago. However, in the long run, measures have to be taken against the discharge of nuclear fuel. According to an expert of the Atomic Energy Commission, it would take around 30 years for the complete containment of the Fukushima Daiichi accident. There are many matters which have not been experienced so far. Atomic energy experts as well as the best brains from the world over must come together to find the solution to this problem. The government is working towards forming such a system.

When we talk about the area outside the nuclear power plant, the contamination is spreading and a feeling of insecurity has developed amongst the citizens. Hence I think it is necessary that the government and the power company should have a deep sense of responsibility and should search their conscience. I think that the contamination outside the nuclear plant would not affect the health of the citizens. I, however, am extremely sorry that the entire country has fallen into despair due to this.

The government now is trying its best for decontamination. First of all, it is important to provide accurate information for monitoring. Disbelief still exists in the figures provided by the government. The government is putting in effort, but there might be problems in the approaches adopted. The style of communication is bad, the efficiency is poor, the process is not well designed; hence the residents are not feeling relaxed as yet. ICRP is also stating that the residents should be taken into confidence and then decisions should be made together. However the scene has not yet changed. Things are decided by the scientists all by themselves and then they are simply conveyed. The decision making process is not convincing. Therefore there exists a sense of distrust. And this has to be changed.

In the case of decontamination, the standards for external exposure (to radiation) have been set. The annual external exposure of any area should be less than 20mSv. If this isn’t the case, people are not permitted to live there. However if it is less than the set standard, the residents can return to their homes. Hence, in the short run it is important that the areas with external exposure of 1~20mSv are decontaminated and made available for the residents. At present, data collection for decontamination has been stopped. It would, however, being full scale from April. As far as decontamination is concerned, there are challenging topics such as the hot spots (the area where the radiation dose is high locally) being jumbled up and the contamination levels desired by the agricultural people and those desired by the common man are different etc. Normally, monitoring is required to be done along with the residents before the decontamination. However it could not be done in this case. In addition, the present grid of monitoring is oversized. If possible it should be done within 100 meter ×100 meter. Even this is not feasible due to shortage of manpower. We would like to collaborate with various people and find out the best approach.

In the long run, it is necessary to differentiate between areas where residents can return and those where they cannot. This should be done at the earliest possible time. However, this needs a political decision. The residents build up expectations when the scientists state that “decontamination is possible”. However the areas where residents cannot return need to be clearly decided with the judgment of experts.

In addition, the citizens have a sense of distrust concerning the safety of other nuclear power plants. This was a tsunami and earthquake beyond the control of the safety standards. Hence now new standards should be created which would factor in such disasters. And the nuclear power plants must comply with these new standards. It is very difficult to create new safety standards in a short time span. Therefore, a stress test needs to be conducted. It seems that easy-to-follow restart criteria are not yet given. I think it is not necessary from an energy demand and supply point of view. However, if a new regulatory agency is formed then it would specify the standards of restart for the nuclear plants which are not operational at present. The new regulatory agency would do its best to convince the residents and make the nuclear plant operational.

Future energy policy of Japan

As far as energy policy is concerned, in the short run, the demand and supply measures for this summer must be formulated. Relevant data is now being collected. Investigations are also being made on the assumption that electricity generated using nuclear power would be zero.

In the long run, the only decision that has been made is that dependency on nuclear power plants would be reduced.  Discussion over the future energy mix is not clear. The government has promised that it would provide the alternatives by this spring and things would get decided with a national debate in summer. As national debate is a new concept, it would require cooperation from the government as well as the entire nation including experts from various fields. We need to urgently find a process which would convince everyone that “The decision was taken after a debate”.

A significant philosophy needs to be formed to decide the energy mix with certain standards, as a society. I think apart from the debates by the government commission, it would be better if the debates are done everywhere and communicated to the government at the end.”

※ SMCJ Comment: Tatsujiro Suzuki was associated with sociological studies of science and technology through technology assessment research. He is also active in interaction with the society. Hence, in Japanese organizations where there is a strong tendency of confining issues bureaucratically, he is considered as a significant spokesman of Cabinet office Atomic Energy Commission.

———

Assistant Professor Hiroaki Koide is from the Kyoto University Research Reactor Institute

“Things which have been learnt one year after the Fukushima disaster

We’ve realized that we don’t know anything. If the accident was at a thermal power plant, it would have been possible to inspect the actual accident site and find out the details. However, in the case of a nuclear power plant disaster it is not possible as there are radioactive materials. The people who were promoting nuclear power generation so far say that the disaster was “unanticipated”. As the accident was unanticipated, the measuring devices required to investigate the cause of the disaster are also not installed. Furthermore, the so-called measuring devices which were installed have broken down. It is of utmost importance to know the whereabouts of the nuclear fuel, and the melted reactor core. These facts however are not known.

Future prospects

If we talk about the scene at the nuclear plant, then the problem is that we don’t know the extent the melted reactor core would spread to. It would be important to know the kind of measures that would have to be taken to prevent the spread of the contamination. If the melted reactor core drips underground and comes in contact with groundwater, radioactive material would spread in the environment. Therefore, it is important to set up barriers beforehand and prevent such contact.

Another problem is the spent nuclear fuel in the pool. Daiichi reactor 4 has been badly damaged. Efforts should be made to prevent further damage to this pool. This, however, is difficult due to frequent aftershocks and the high radiological dose levels. In the event of a big aftershock and the pool breaking down, the spent nuclear fuel would spread in the environment in the absence of a barrier. The workers have already started clearing up the debris. Moreover TEPCO might be looking at this problem as a top priority.”

※ SMCJ Comment: Hiroaki Koide is considered by the Japanese media to be a pioneer among the experts who have adopted a stance supporting denuclearization. He has mentioned his stance in a well-known Japanese national daily as well as in weekly magazines. He is in the limelight in the alternative media.

———

Assistant Professor Tetsuo Sawada is at Research Laboratory for Nuclear Reactors Energy Engineering at the Tokyo Institute of Technology

“Various events occurred within a week of the disaster. If the systems before the disaster are compared with those afterwards, does it develop as expected? If the condition of the reactor core is taken into account, then the fuel of the reactor cores is damaged from Daiichi reactor 1 to Daiichi reactor 3. And a significant proportion of the core fuel has melted. It is not very clear about the exact quantity of the core fuel that is damaged and whether it has spread in the furnace. There is a possibility that some fuel might have leaked out of the containment vessel and some quantity has melted. I think there is no marked change according to the circumstances reported by the Tokyo Electric Power Company (TEPCO) a few days after the Fukushima disaster. For example, if Daiichi reactor 1 is taken into consideration, then it is not clear whether the percentage of the core fuel that has melted is 70 or 100.

The problem of contamination and decontamination of any region due to radioactive material is a serious issue. It has been confirmed that in late March radioactive material was dispersed in areas including Itate, Fukushima Prefecture. The quantity of the discharged radioactive material and the dispersed radioactive material distribution has not changed a lot since then. Major emission into the environment stopped immediately after the disaster. However, the problem is coping with the substances that have already been discharged. Air dose rate observed in Minamisoma and Itate has not yet reduced. The matter has become serious as the circumstances are very difficult to comprehend and deal with. And it can be said that now the seriousness of the matter has increased from last March-April.

There is one more point which needs to be considered seriously. Areas within a 20-kilometer radius of the plant have been left uninhabited. This area was declared as a ‘no-go’ zone. However, this area has been neglected over the past year. The rubble caused by the tsunami and the wreckages of houses due to the earthquake etc. are all lying untouched.  If the situation continues like this then there would be much deterioration and decay. Furthermore, if there is new vegetation growth then it would advance the immobilization of the radioactive material. It has been also heard from the residents who have returned that the circumstances are getting worse due to the stand adopted.

How does one process and control the radioactive material that has been discharged into the environment? How can the people from the affected area cope with the radioactive material? These issues are very important. However, their solution is difficult. There was some information available from the knowledge gained following the Chernobyl accident, regarding the discharge of cesium in large quantities. However, I now comprehend the present circumstances and their gravity, after my frequent visits to Minamisoma and Itate, listening to the tales of residents after the actual discharge. It can be said that even my thoughts have changed.

An atomic energy regulatory agency is to be established in April. It seems that though the organizational structure of the agency would change, the content would be almost the same. I, however, am not clear as to how it should be. Neither am I in a position to comment on it. The future concern is the measures for the Daini power plant. There are frequent big earthquakes in this area following the earthquake in Sumatra in 2004. The possibility of a future earthquake of the same magnitude and that could possibly lead to a tsunami also exist. If such a situation occurs then the Fukushima power plant will become even more compromised. The circulatory system of the cooling pool of the reactors need to be maintained. It is necessary to have preventive measures in order to maintain the present cold shutdown, just in case something else goes wrong.

Lastly, there is another concern regarding the water shielding wall. At first, there was a situation when the water accumulated in the reactor building and the trench would not lessen even after being pumped out. The chances of groundwater leakage have been stated. Therefore it was decided to build a water shielding wall as a temporary measure. Since it would cost approximately 100 billion yen to build it, TEPCO took the stance that it would only build it if it got support from the Government. As a result the plan was cancelled. Even at this point in time, the relation between the groundwater flowing under the power plant and the water flowing outside it is not known. There might not be a leakage of contaminated water on a large scale. The question of quantity remains. I think there is a possibility of leakage being present at the moment.”

※ SMCJ Comment: Tetsuo Sawada faced the media as an expert after the earthquake disaster and tried to explain the situation. As a result, he became popular as ‘a scholar beholden to the government’ on the Internet. However, at present, as one of the founders of the Minna-no (Everybody’s) Energy and Environment Conference (MEEC, http://www.meec.jp/ (only in Japanese), he is participating in a debate for social decision making regarding future energy policies including alternative energy.

———

Useful links:

Information on an International Expert Symposium in Fukushima held last September:

http://www.nippon-foundation.or.jp/eng/media/news/2011/20111114.html

Stream of the symposium (which was followed by a large scale press conference):

http://www.ustream.tv/recorded/17194336

Published conclusions and recommendations:

http://iopscience.iop.org/0952-4746/31/4/E02

The March issue of Journal of Radiological Protection has most of the presentations as short papers:

http://iopscience.iop.org/0952-4746/page/Forthcoming%20articles#Notes:_SelFukushima_

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Feel free to use these quotes in your stories.  If you would like to speak to an expert, please don’t hesitate to contact us on (08) 7120 8666 or by email.

Australian expert nuclear comments

Australian expert tsunami comment

UK expert comments

Canadian expert comments

There is a separate Round-up for Japanese expert comments here.

Useful links

AusSMC hosted an online briefing on this issue earlier today with Japanese, UK and Australian experts – a full copy of the briefing is available here

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Nuclear comments

Tony Irwin is a Chartered Engineer and is a visiting lecturer for the Masters course in Nuclear Science at the ANU. Tony is the Chairman of the Engineers Australia Nuclear Engineering Panel. Tony worked for British Energy in the UK for more than thirty years commissioning and operating eight nuclear power reactors. Following the Chernobyl accident he was a member of a World Association of Nuclear Operators (WANO) mission that reviewed operating practices at Russian RMBK reactors. In 1999 he moved to Australia and joined the Australian Nuclear Science and Technology Organisation (ANSTO) and was Reactor Manager during the construction and operation of the OPAL research reactor; he retired from ANSTO in late 2009.

On the sequence of events:

We now have a better understanding of what happened :

Event Sequence – Key Events

*Estimated                                            source: Tony Irwin

- First core damage estimated to have occurred within 4 hours of the earthquake and reactors 1,2 and 3 cores largely melted within the first 3 days

- Hydrogen explosions caused the main damage and release of radioactivity

- Reactors stable within 2 weeks

On the Fukushima site today:

“The four damaged reactors are in a stable cold shutdown state, cooled by water circulated through a treatment plant. Site clean-up, including removal of radioactive rubble, continues. A mid and long-term roadmap for the decommissioning of units 1-4 was issued in December 2011. Phase 1 prepares for the removal of spent fuel from the cooling ponds to commence by 2013. Phase 2 prepares for the removal of fuel debris from the reactor core to commence within 10 years. The final phase completes the decommissioning of the reactors in 30-40 years.

There are still over 100,000 people evacuated from Fukushima Prefecture. In the areas within the 20km evacuation zone with an annual radiation dose of  <20mSv/year, it is expected that people will be allowed to return in March 2012. For higher radiation areas, remediation is required before restrictions are lifted by perhaps 2014.”

On nuclear power in Japan today:

“Before the accident, there were 54 reactors operating in Japan supplying 29% of the electricity demand.  Since the accident, as reactors have been shut down for routine inspection (every 13 months) they have not been allowed to restart pending a comprehensive assessment of the response of individual reactors to extreme accidents (‘stress tests”). To date, the Japanese safety authorities have not approved the restart of any reactor.

As of March 2012, there are only 2 reactors operating. Japan trade deficit is at record levels as fuel imports have soared.”

On the world situation:

“The severity of the accident and the need to ensure reactor safety in extreme events was recognised worldwide. Germany took the political decision to immediately shutdown 8 old reactors, and all reactors by 2022. Most countries announced plans to continue with nuclear power and assess the safety of their reactors. For example, the UK has confirmed the safety of their existing nuclear power plants and has recently approved design certification for two types of new reactor to be built in the UK.”

On lessons learnt:

“Reactor cooling is essential and must be maintained irrespective of external conditions. Modern reactors, for example the Westinghouse AP-1000 have passive cooling systems that require no external supplies and would have survived even this severe accident. The safety of existing reactors is being assessed to ensure they have diverse and physically separated cooling systems and electrical supplies.”

———–

Dr Don Higson is a retired nuclear safety specialist and Fellow of the Institution of Engineers Australia, Fellow of the Australasian Radiation Protection Society

On Engineering

“At Fukushima Daiichi, the reactors shut-down safely when struck by the fourth largest earthquake ever recorded. The nuclear emergency was due entirely to loss of on-site power supplies when the power station was inundated by a much larger tsunami than had been anticipated in its design. Clearly, the design of nuclear plants against the risk of flooding needs to be brought up to the level of design against seismic risk.”

On the health effects

“Rating the nuclear accident at Fukushima as 7 on the International Nuclear Event Scale (INES) has given the misleading impression that it was as bad as the Chernobyl accident. At Fukushima, no physical health effects of radiation have been observed among the general public and effects on workers have been far lower than those at Chernobyl. The INES was meant to aid public understanding of nuclear safety but has, in fact, made it more confused. The INES should be substantially modified or scrapped.

As at Chernobyl, the major public health effect of the Fukushima accident has been psychological, due to the forced relocation of population and exaggerated fears about radiation. In such circumstances, the public must be evacuated from the area as a precaution when it is not known how the situation will develop. However, they would be better off being allowed to return to their homes once it is certain that the situation is under control and that potential exposure levels are no greater than 20 mSv/y. Many people in the world are exposed naturally to higher levels of radiation than this without discernible adverse health effects. It is counterproductive to behave as though 20 mSv/y is a dangerous dose rate.”

On the safety of nuclear power

“Outside the former USSR, the nuclear industry continues to be one of the safest industries in which to work and the safest way to generate most of the electricity the world needs.”

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Dr John Price is currently a consulting engineer.  He was a member of the Safety Policy Unit of the National Nuclear Corporation UK where he studied major nuclear power accidents.

“After the Three Mile Island Accident of 1978, people like me who advocated nuclear power said two things about that incident: the safety systems at the station had contained the radiation and that ‘lessons had been learnt’. What Fukushima demonstrates is that no lessons are ever really learnt. These lessons are many and deep. As an example, there was a very practical lesson from Three Mile Island. Once the fuel cladding overheats, the zirconium metal in the cladding reacts with water to produce hydrogen gas.

The appearance of hydrogen gas during the accident at Three Mile Island caused major alarm, though in the end no damage. So why was no lesson learnt?  At Fukushima the buildings of reactors 1 and 3 actually exploded violently while the world watched on television. Unit 2 also probably had a hydrogen explosion inside its containment and this may have caused leaks. Why, given the events of 1978, were the plants at Fukushima, and indeed nuclear plants worldwide, not fitted with the fairly simple means of dispersing hydrogen gas to prevent explosion?

I regard the damage caused by the hydrogen explosions to be the main reasons why recovery from the Accident at Fukushima will take a much, much longer time than some suggest. In a statement that went viral around the world in the week of the Fukushima accident, I said that clean-up will take 50 to 100 years. I still think this is the likely timeframe.

There have been other, more fundamental lessons which were not learnt. Can there ever be proper regulation of Nuclear Power, or indeed any other major risk? Are not the regulators always part of the cause of the accident? For non-nuclear examples, think of the Gulf of Mexico oil spill. Think of situations where people are permitted to build cities in areas subject to Tsunami. Think of recent financial crises. Whoever authorises something also has responsibility for its consequences. They own the benefits and they own the disasters.

Once the plant was agreed to be built, there were many bargains struck between the Japanese regulatory authorities and Tepco, the owner of the Fukushima plant. No matter which government department had been the regulator, no matter how independent the regulator might have wanted to be, compromises had to be made.

Here are some questions which we might hope should have been asked during regular licensing discussions:

• What emergency equipment should be provided for accidents beyond the design basis of the original design?
• What was to be the size of the Tsunami protection?
• Should Fukushima Units 1-4 have been operating in 2011?

All of these questions have associated major costs, whatever the answers. In each of these discussions, the regulator would want more and more expensive things, and Tepco would seek a financially possible compromise.

The last question, as to whether Daiichi 1-4 should have been operating in 2011, seems to have the easiest answer. No. It was an old superseded plant, in the wrong place. Fukushima Daiichi Unit 1 started operation in 1971 using 1960s designs. Units 2 to 4 also used the same design, though they are slightly larger. By the late 1970s, the designer of this type of plant, GE of USA, had already replaced Daiichi’s Mark 1 design of reactor with a design that they said was safer. By the 1990s even safer plants were being offered.

In retrospect, the decision as to whether the units should have had their licenses extended seems reasonably easy for Japan in the 1990s. Replacement could have been planned, new and safer plants could have been built. And nuclear energy would still be fulfilling its promise for Japan. Instead, a different decision was made. They fitted new tyres to their 1971 banger rather than buying the newer and much safer model. I assume that we will eventually find out what happened during regulatory discussions about the Daiichi plants in the 1990s. Whatever did happen in these discussions, the wrong decision was made for Japan, and for the world.”

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Dr Pradip Deb is a Senior Lecturer in Medical Radiations at RMIT University

“The Fukushima Daiichi accident has been one of the two major accidents in the international nuclear and radiological event scale (INES) in the last twenty five years (the other one was Chernobyl). The latest IAEA (international atomic energy agency) status report shows that the estimated external doses to the public from the cities within 20 kilometres from Fukushima Daiichi reactors are within the acceptance level for the public (1 mSv). Food monitoring data shows that in more than 99% samples (based on 14344 samples) the radioactive caesium and iodine isotopes (Cs-137 & Cs-134 and I-131) are within the acceptance level.

It is not practical to say that the world should be free of nuclear power. The next generation power reactors will be safer. The lesson we have learnt again is that it is radiophobia that harms us psychologically more than actual radiation doses do. Not only in the developing countries, but also in the technologically advanced countries, people are likely to believe unscientific reasoning about the effects of radiations. Topics of Radiation physics are currently not included in the school curriculum in most of the countries in the world, not even in Japan. To reduce radiophobia, the radioactivity and their effects should be understood by the general public. One way to make the public more trusting of radiation issues is teaching radiation physics starting from the school level science education.”

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Tsunami comment

Professor James Goff is Director of the Australia-Pacific Tsunami Research Centre and Natural Hazards Research Laboratory, University of New South Wales.

“A year on from the 2011 Tohoku tsunami and we are still asking questions, more than we have answers to. I have been invited by Tohoku University in Sendai to attend a special ‘One-year Memorial of the 2011 Tohoku Earthquake and Tsunami Disaster’. This will happen on the same day as a ‘Forum for International Research Collaboration’. This will be the fourth visit by people from our centre. First in May to carry out some of the earliest international research on the tsunami – how big it was, what it left behind and so on. We visited again in August to revisit this work and to see how things had changed. Currently a member of our team, Dr Catherine Chague-Goff, is also on a Visiting Professorship to the University of Hokkaido. Why so much commitment? Essentially because we want to help the Japanese to understand the 2011 event, its precursors and other events in the region. However, we are also committed to helping our Japanese colleagues. Our centre has skills that the Japanese are interested in exploring and we are keen to work in collaboration with them to make this happen.

What have we learnt so far? Well, one of the more interesting finds in that for nearly 50% of its inundation distance inland the tsunami left almost no sand deposit, just mud and debris. Who cares? Well, if you are looking at how big and how often these events have happened in the past – you need to look for more than just the sand or else you might under-estimate things. Hence the interest in our work and what we have done elsewhere. We have also learnt a lot about the longer term after effects of these events. What one might call the ‘what are things like on the ground one year on’. Yes, much of the debris has been being cleared up, yes much of the evidence of destruction has been erased by diggers and work crews, but what seems a minor point is starting to become an issue – there is still a vast amount of salt in the soil and rice doesn’t like salt – and so in these places crops are hard to grow. There are implications here for long term recovery. Add to this things such as the loss of communities, poor roads, contaminated land and the sheer enormity of the devastated area and you can see that there is no simple fix.

We are returning to Sendai again to start putting the 2011 events in context. We really do need to know how big and how often these events occur because we don’t want to under-estimate the next one, not just in Sendai but for the whole of Japan. We also want to take these lessons with us to the rest of the Pacific so that we can do a better job there as well. Whether we can achieve this quickly or not remains to be seen. We all still have lots to learn.”

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UK expert comments

Dr Jim Smith, Reader in Environmental Physics, University of Portsmouth said:

“When the first measurements began to appear of contamination levels in land around Fukushima, it quickly became clear that evacuation of the population would be for the long term. Several hundreds of square km of land have radioactive caesium levels similar to those seen around Chernobyl, so clean-up is an enormous, perhaps impossible, task. Experience from Chernobyl showed that, with massive effort, decontamination of towns can be successful by re-surfacing roads and skimming off contaminated topsoil from lawns.  But clean-up of large areas of fields and woodland wasn’t even tried because of the huge expense and amounts of waste it generates. More likely, as at Chernobyl, large areas surrounding Fukushima will remain contaminated for decades, some areas probably too contaminated for people to return to their homes.

If a Chernobyl-style permanent exclusion zone is set up at Fukushima, will it be a nuclear wasteland, or will nature reclaim the abandoned lands ? There are already reports of bird populations being damaged by radiation at Fukushima, but trying to separate the relatively small impact of radiation from all the other factors which affect animal populations is tricky. At Chernobyl, 25 years on, we have seen – often contradictory – evidence of long-term damage to wildlife, but also reports claiming the area is like a nature reserve because people are no longer hunting , fishing or farming. In 1996, Belarussian scientists even introduced the rare European Bison into the exclusion zone and the population is thriving, as are other large mammals such as deer, wild boar and wolves.

We can’t yet say what the future of the Fukushima exclusion zone will be until we know how far decontamination is possible, and how much residual radiation the evacuees are willing to return to. But my guess would be that we’ll see another permanent exclusion zone – much smaller than at Chernobyl – which eventually will return to nature. And, as at Chernobyl, in 25 years’ time scientists will still be arguing about whether the radiation is doing long term damage to the wildlife it contains.”

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Professor Richard Wakeford, Visiting Professor at the Dalton Nuclear Institute, University of Manchester said:

“There can be no doubt that the accident at the Fukushima Dai-ichi nuclear power station has caused genuine concern among those living in Fukushima Prefecture, and throughout Japan, about the health effects resulting from exposure to radiation from the radioactive materials released into the environment. Ordinary people are not experts in radiation risks and their fears are driven by what they know of the radiation effects seen after the atomic bomb explosions at Hiroshima and Nagasaki and after the Chernobyl nuclear reactor accident. Unfortunately, some comments that have been made in the media have unnecessarily increased public concern.

That the Fukushima Dai-ichi accident was very serious is beyond dispute, and the reasons for it must be fully investigated. However, in an accident such as this, the consequences can be limited by appropriate actions to control exposure to radiation. So, unlike at Chernobyl, there have been no deaths or early health effects among the emergency workers because their doses were carefully limited. The only clear direct health effect among people living around Chernobyl is thyroid cancer in those heavily exposed as children to radioactive iodine – this was mainly due to the children drinking heavily contaminated milk because a food ban was not introduced quickly enough by the Soviet authorities. Measurements of radiation from radioactive iodine in the thyroid glands of children living near Fukushima Dai-ichi indicate that monitoring of the environment and the banning of consumption of foodstuffs where necessary have avoided this problem of high intakes of radioactive iodine. The main component of radioactive iodine (iodine-131) is short-lived, effectively disappearing from the environment after three months, so this problem has now passed.

The major issue for contamination of the environment now is radioactive caesium (caesium-134 and caesium-137), which exists in the environment for much longer than radioactive iodine. So, monitoring of radiation exposure and contamination of foodstuffs will have to continue for some time. Modern radiation measuring instruments are very sensitive, and it is possible to detect very small levels of radiation and radioactivity – for example, it is still possible to detect very low levels of caesium-137 in food from Chernobyl contamination and fallout from nuclear weapons testing. What matters is the levels of radiation and radioactivity, since radiation and radioactivity are a natural part of the world in which we live. Measures can be taken to reduce the amount of radioactive caesium in the environment (for example, by removing topsoil) and in foodstuffs (for example, by monitoring items of food from contaminated areas), so keeping radiation exposures to acceptable levels.

By ensuring that the damaged reactors at Fukushima Dai-ichi are stabilised such that further significant releases of radioactive materials are very unlikely, by the judicious removal of radioactively contaminated materials from areas used by people (for example, areas in villages and towns), and by the careful monitoring of radioactive caesium in foodstuffs, the risk to health from the Fukushima Dai-ichi accident can be reduced to a level that for the great majority of people in Japan is very small compared to the risks experienced in everyday life, including the risk posed by other sources of radiation and radioactivity (mainly natural sources) that are part of the everyday existence of everyone in the world.”

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Professor Paul Hunter, Professor of Health Protection (University of East Anglia) and Editor of the Journal of Water and Health, said:

“The Japanese have put a lot of effort into rebuilding the main roads through the affected areas and clearing away the rubble. There are mountains of rubble waiting to be sorted and then sent to landfill (the rubble contains many valuable metals such as iron etc. that they will not want to waste). This will take quite a few years to complete. The main WWT plant that we visited is now able to do primary treatment and chlorination but will not be back to full effectiveness for about 4 years, though when complete will be a state of the art plant much improved on the old one.

There is a major problem with rebuilding in some areas in that after the tsunami receded it took with it sediment and the land dropped 40 to 60 cm in many places which makes a lot of the land below the level of high tide. So issues with building sea walls or raising land levels. Indeed the rebuilt road have been raised up

Another problem is that the rubble mountains are fermenting and are at risk of developing spontaneous fires.

As regards infectious disease epidemiology, there does not appear to have been major problems although my colleagues are concerned about the impact of inadequately treated sewage discharge to sea and are monitoring the situation.”

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A reflection on the media coverage one year on

Professor Malcolm Sperrin, Director of Medical Physics at the Royal Berkshire Hospital in Reading , said:

“The Fukushima incident rightly caught the immediate attention of the media and led to discussions and debate about numerous aspects of nuclear power, safety, command and control following major incidents and also the perception of risk to name just a few. The level of commentary was generally balanced although there were some instances of conspicuous scare-mongering albeit generally based on poor initial information provided to the media.  The events that evolved over the months following the tsunami were often easy to explain for experienced and knowledgeable scientists. It is too easy to condemn facts and subsequent interpretation that we as scientists feel have been explained incorrectly in the media, it is essential that we maintain an awareness of how specialised some of this knowledge is. I also feel very strongly that we have a moral duty to provide, accurate, timely and digestible input to assist in the understanding of the population as a whole.

My specialisation falls into the broad division of radiation medicine and hence I had a role to play in interpreting the population risk from exposure to the released radiation. To me, the risk mitigation comprised the three tenets of time, distance and protection and with this in mind everything that could have reasonably been done by the Japanese authorities was done. The explanation of any risk that was present was far more difficult in that at low radiation doses, you cannot specify who will receive a health detriment or even what that detriment is and it was occasionally stated by some that such lack of precision was equivalent to ambivalence or even clandestine shrouding of the facts. It is my job to ensure that everything is done to measure and mitigate radiation risks and such accusations did occasionally hurt.

However, I do feel that as experts in relevant fields, we also have a clear responsibility to take concerns seriously and furthermore we must have the tact, social feelings and adaptability to ensure our points are understood

In summary, I feel that the [UK] media did an excellent job and repeatedly stated the need for accurate and timely comment. It should be borne in mind that the tsunami killed tens of thousands and has received relatively little coverage.”

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Canadian expert comments

On the Earthquake…..

John Cassidy
Research Scientist, Natural Resources Canada (Earthquake Hazards)

Japan had about 30 seconds of warning for the quake. Is 30 seconds of warning for a quake typical? Or how has the ability to project earthquakes changed recently?

Thirty seconds – that depends on distance – it’s not a prediction but really taking advantage of the fact that it takes seismic waves time to travel. So if a large earthquake happens right beneath your feet, or ten kilometers away, you have no warning. But if you have an earthquake about a hundred kilometers away, or further away, then you can have upwards of 20 or 30 seconds of warning. In a subduction zone we have these really long faults, and that’s area where you can actually have the longest warning time. If a subduction quake started in California and ruptured up towards us, it might actually take 4 or 5 minutes before the shaking reached Vancouver or Victoria. In Japan, the earthquake was offshore – in Tokyo they had about 30 seconds of warning. You need to have lots of instruments on the ground, automatic systems in place, and then you have to have systems in place to transmit and use that info – to media, to individuals. And that system was just being tested in Japan, and it actually worked really well, saving many lives. At the time of quake there were about 20 high-speed bullet trains that were stopped by this system. All of them were safely stopped – stopped from going into tunnels, over bridges, they shut down the trains, the nuclear power plants. Of course what didn’t work was the tsunami, which was much higher than planned for. This monitoring system is still being developed, and it’s not completely operational yet, but there’s really good promise from Japan that these systems can help save lives.

What kind of warning for such a quake could we expect here on the West Coast of Canada? Or indeed in Eastern Canada?

In Canada it really depends on where the quake occurs relative to cities. In a subduction zone like Cascadia, that’s where you have the possibility of anywhere from 20-30 seconds to a few minutes of warning. In Eastern Canada it depends on exactly where the quake occurs but you’re probably looking at up to 10′s of seconds.
Typically, a smaller earthquake is not going to cause damage, so you can look at a distance and magnitude combination and calculate where you’ll benefit from early warning. Often, if the earthquake occurs at greater than 100 kilometres away it doesn’t cause damage unless it’s over about 7.0 magnitude.

Can you explain a bit further why the tsunami was larger than expected?

This was the very first time that a giant subduction earthquake (magnitude 9) has been recorded in such detail. In Japan literally thousands of instruments recorded it, and provided detailed images of how the ground shook and moved. Using this data, you can work backwards and see how the displacement moved along the fault, up to 40 metres in some cases, and you can see where the plates slipped and didn’t slip.
What we discovered was that there were large movements at shallow depths, where the plate begins to bend. But these shallow depths produced about 40 metres of slip, and it was this shallow slip that generated the tsunami. It is believed that a key reason for such a large tsunami is this large slip. A key lesson from this quake is that understanding the region where these plates are interacting — which typically is offshore in areas such as Chile, Mexico, Japan — and getting instruments onto the seafloor to monitor – is critical. One of the questions that always crops up is, was there any signal that this magnitude 9.0 quake was about to happen? Having instruments on the seafloor is one of the best ways to do that because then you’re not limited by stations onshore that are 100 to 150 kilometres away from the action.

That leads into a lot of the studies we have underway, with Neptune Canada for example, which is a joint University of Victoria project with Natural Resources Canada. It’s the world’s first real-time seafloor observatory at a regional scale. For the first time we have seafloor seismographs, pressure gauges on the seafloor right above that locked fault zone. Natural Resources Canada scientists in Sidney, BC also have projects underway with Japanese colleagues, and we have these instruments on the seafloor just west of Vancouver Island, looking for small earthquakes, looking at the structure of the plate as it begins to dive beneath Vancouver Island, and looking at where energy is stored — little hotspots where we might see stronger shaking if we have a subduction quake in the future.

In Japan, there are plans for drilling into the subduction fault zone. An international ocean drilling program is sending their drilling ship to the region offshore, where the quake occurred, and they’re going to drill through oceanic crust into that fault zone. That will be the first time ever. In the ocean it will be about 7 kilometres down to the seafloor, and then they have to drill through about a kilometer of the ocean plate to reach the fault, and that will be underway later this year.

They’re hoping to see for the first time one of these subduction zones where the fault is, what happened where the slip took place. One of the things they should get from drilling is what is the material like along the fault zone, how does it store energy, and how often do these large quakes occur along that fault zone.

NRCan scientists are also working with US colleagues – and are planning  to deploy tilt-meters on the sea floor off Vancouver Island, Washington, and Oregon – to look for very subtle movements of that ocean plate. Are there things happening that we can’t see and can’t record with seismographs? These sensors will record tilting, looking at very tiny, and slow movements.
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**Michael Bostock
Earthquake Seismologist, Department of Earth and Ocean Sciences, University of British Columbia
More info on Michael Bostock

What we have learned from the Tohuku earthquake?

We still have much to learn about large earthquakes. But in terms of the stories coming out of this particular earthquake, first of all, this was not expected. In the last thousand years or so, records of earthquakes off Honshu, the island that was affected, have been in the magnitude of the 7 to 8 range. They occur regularly, and most of the structures and building codes are designed to meet that type of earthquake threat.

This particular earthquake in March 2011 was unusual. Generally the size of an earthquake is measured in terms of magnitude. That’s related to a couple factors: the strength of the rocks on either side of the fault, the size of the area of the fault that actually ruptures and the actual slip or displacement of the fault.

What made the earthquake that occurred last year at this time interesting is that it was actually a cascade of many smaller earthquakes, the total of which is greater than each individual quake. Basically what happened is there are parts of the fault called asperities that “stick”, and that can occur for a variety of reasons, but that’s where earthquakes are generated. Around the asperities, we think, the plates are moving smoothly. So gradually over time, strain and stress builds up in these asperity areas, whereas the rest of the plate is moving normally. So what happened last year is that a large rupture on one asperity caused the rupture of many other asperities, so that a cascade of many small earthquakes occurred – the total of which, in a way, was greater than the sum total of the individual parts.

So if you look back in historical records, you see that similar sized earthquakes have happened early in the previous millennia, the last one in that region occurring about 869 AD. Unfortunately the historical information came a little too late, but this has opened the eyes of seismologists and raised awareness that we can have superquake cycles within cycles of regular earthquake cycles.

There’s been a regular pattern of these smaller magnitude earthquakes over an approximately 50 year cycle, but we can have superquake cycles that encompass the regular cycles, that is closer to approximately 1000 years. This is one thing that we’ve learned.

Another thing we’ve also learned from the Tohoku earthquake has to do with subduction.  These major subduction zone thrust faults correspond to one plate – an oceanic plate — plunging beneath another continental plate, and it happens offshore in Japan and also here in southwestern BC.

The surface where the two faults meet is called the trench. This submarine trench or valley tends to get filled with sediment, like it is here off the west coast of Vancouver Island. And it has been thought that because the upper portion of the fault juxtaposes sediments against the downward moving plate, that it makes that part of the fault softer, and therefore causes it to slide more continuously. So it was thought that there were not great prospects for major displacement. And it was thought that there would not be an opportunity for asperities. But that assumption definitely wasn’t valid for Tohoku.

The assumption was that the displacements weren’t going to be as large as they actually were – when in fact they were the largest displacements ever recorded — on the order of 60-80m. That means one side of the fault moves with respect to the other side of the fault, by 60-80m. If one side is moving up, and the other side is moving down, that means the water column is being shifted by tens of metres. That means the water column, with gigatons of water, is being shifted by tens of metres. It’s a bit like in the bathtub if you were holding a basin underwater and then you lift it up — that’s what drives the tsunami. So the larger the surface displacement, in these deep ocean floor earthquakes, the larger the tsunami is going to be.
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John Clague
FRSC, Shrum Research Professor, CRC Chair in Natural Hazard Research, Department of Earth Sciences, Simon Fraser University; Emeritus Scientist, Geological Survey of Canada.
More information on this expert

“This earthquake raised some interesting questions because the Japanese were not expecting an earthquake so large. They knew that subduction zone earthquakes occur along that part of the Japanese coast. A subduction zone occurs where two tectonic plates move towards one another, and where they meet, one slides under the other. This particular quake released about 30 times the energy of the largest (ca. magnitude 8.5) event that Japanese seismologists thought was possible. Geologists, however, had found evidence of infrequent prehistoric tsunamis that were larger than could be produced by a magnitude-8.5 subduction zone earthquake. This size earthquake seems to recur, on average, about every 1600 years or so and involves larger slippage along the mega-fault that separates the Pacific plate from the plate that underlies northern Honshu. Unfortunately, the geological information had not yet found its way into the planning process in Japan.

This was the largest earthquake in Japan’s recorded history.

The Japanese had previously experienced earthquakes of magnitude 8, but nothing close to the February 2011 quake.

So what are the implications of the Tohoku earthquake for Canada? A subduction zone similar to that off the coast of Japan exists off in Cascadia. Scientists have shown that very large earthquakes, in excess of magnitude 9 and involving slip along the entire length of the subduction zone from central Vancouver Island to northern California, happen in Cascadia and have similar effects to the Tohoku earthquake. What became clearer after the disaster in Japan is that large, potentially damaging aftershocks occur for weeks or months after the main shock of these huge subduction zone earthquakes. We need to plan for aftershocks in the Pacific Northwest.

Examining what happened in Japan doesn’t give you specific details as to what would happen on the west coast of North America, because no two subduction zones are identical. It depends on a lot of things like the temperature of the subducting plate and the presence and distributions of asperities — meaning “sticky” patches along the fault that resist sliding. Japan’s experience with subduction zone earthquakes, however, does illustrate the range and complexity of these events.

The other interesting thing that we understand here on the West Coast of North America, which apparently the Japanese did not consider, is that the land subsides 1- to 2 m over a very large area of the coast when these earthquakes occur. The Japanese had built their tsunami defence walls to deal with waves of a certain height, but the freeboard — the height of buildings and infrastructure above the water level of the ocean — was reduced by 1-2 m because the land subsided this amount before the tsunami came ashore. The tsunami was bigger than anticipated, but it didn’t help that the Japanese officials hadn’t factored in the loss of 1-2 m of freeboard just due to the earthquake itself.”

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On the nuclear crisis:

Jeremy Whitlock
Reactor physicist at Atomic Energy of Canada Ltd.’s (AECL) Chalk River Laboratories, Manager of Non-Proliferation and Safeguards; Fellow of the Canadian Nuclear Society (F.C.N.S.)
More information on Jeremy Whitlock
A recent paper by Jeremy Whitlock on the future of nuclear power

“I think the thing that strikes me most now is the same thing that struck me in the days and weeks immediately after the tsunami: the degree to which the world’s attention appears to have been diverted almost entirely from the tsunami disaster itself and focused on the accident at Fukushima. This is made particularly stark when one realizes that the Fukushima plant was probably the only major piece of energy supply infrastructure affected by the tsunami that didn’t kill anyone. Mention the tsunami today, however, and the first thing that comes to people’s minds is almost certainly the nuclear crisis, not the 20,000 dead or the incredible loss of property, and to me that’s a sad reflection of the memetic imbalance in human compassion.

A year later we are certain that three reactor cores melted down, and that it was a close call, but what’s not widely appreciated is the degree to which the “robustness” of the technology contributed to reducing the severity of the accident. We had three meltdowns, all within a day or so of the tsunami, but standing outside of the reactor buildings we were not aware of this for about two months – mainly because of the lack of a clear radiation signature. This is a remarkable observation: one of the worst accidents in nuclear history was essentially contained, even with almost total lack of control and safety infrastructure. That is a compelling message that the technical world probably appreciates, but doesn’t go much beyond that eclectic border. This observation includes the contamination of the surrounding region by the way, which is generally at a level that in all likelihood will not likely lead to any negative health effects (this goes for the employees exposed during the event as well). There are places in the world with higher natural background levels of radiation exposure.

This isn’t to imply in any way that the accident at the Fukushima plant wasn’t a disaster, or that lessons weren’t learned (particularly in the area of emergency management) – just to point out a significant skew in the public and media perspective compared to the actual risks. Communication suffered greatly, which contributed to this situation, and in some ways it was the unprecedented application of social networking that did a lot of the damage (increased quantity of information does not necessarily translate to increased communication).

There are two aspects to the emergency management that are relevant: (1) within the station itself (accident mitigation) and (2) beyond the station (emergency preparedness). Lessons were learned on both counts – for (1) the main lessons were ensuring long-term back-up power supply, getting back-up cooling water to the site, proper venting of reactor vessel, long-term cooling of spent fuel; for (2) the main lesson was in communication – conflicting reports, govt control of information flow, giving assurances to the public, providing an effective single point of contact for information flow.

Regarding the effect in Canada, there was a slight disruption in the process to build new stations near Toronto, but otherwise not much of an effect. Even the lessons learned are different here since the CANDU design is already highly resistant to the kind of extended station blackout issue that plagued Fukushima. (Maybe one lesson is that everyone should buy CANDUs!).

To me it would be a step forward if a year later it became widely appreciated that the worst outcome of the 2011 earthquake/tsunami was not the meltdowns at the Fukushima Daiichi plant (in terms of public health and property damage) – however I fully realize that this will not likely be the case; Three Mile Island and Chornobyl both teach us this. 

When I speak on Fukushima I emphasize that the fourth objective of nuclear accident mitigation – after shutting down the reactor, cooling the fuel, and limiting releases – is to communicate effectively.  Fukushima showed how much people can be hurt by hearing poorly communicated information.”

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John Luxat
Professor and NSERC/UNENE Industrial Research Chair in Nuclear Safety Analysis Department of Engineering Physics
More information on John Luxat
A recent paper by John Luxat on the Fukushima crisis

What lessons can be learned one year after Fukushima?

There are things that in my view this event taught us, for example, it reinforced the importance of having an effective containment structure. Clearly, this was breached at Fukushima. With containment breached, there was release of contamination, but, unlike at Chernobyl which had no containment structure,  the radiation releases were significantly lower. Which just reinforces the importance of containment, especially if you factor in Three Mile Island where they had a larger containment than Fukushima that remained intact, and as a result there was no significant radiological impact.

In terms of lessons learned, the biggest lesson is that the industry as a whole needs to look carefully at their emergency response to events that are high impact but low frequency, so-called ‘black swan events’. I believe we need to augment our probabilistic risk assessments with alternate means of risk assessment to handle these kinds of events. Because when you get into very low frequencies, you tend to cut it off, and say that will never happen. I think we should learn from security, military and police, where you deal with challenges where you’re not saying ‘what is the frequency of the event’, but you’re saying, ‘if it happens, what do I do?’ More a deterministic, and not probabilistic, risk assessment would help guide our actions.

Do you think Fukushima had effect on Canada’s nuclear policy and attitudes toward nuclear energy?

I don’t believe it has. For example, if you look at the plans of the Ontario government to refurbish Darlington.

If you look globally, there has been very little change. Aside from Germany, Italy, Switzerland who decided very quickly to stop using nuclear power, most other countries renewed their dedication to their nuclear plans.

So far, what has happened has been more of a response to the economic crisis than to Fukushima. The European debt crisis, for example, has made the economic situation more difficult. Also, in the States there’s been a surge in shale gas resources, and that seems to be driving the energy plans there. Other issues like the issue of climate change, which was dominant in the early 90′s, has taken a back seat.

What should journalists be looking at that they perhaps haven’t looked at so far?

Looking back in retrospect, I realize a nuclear crisis was certainly more gripping as an ongoing crisis, but the relative severity of the crisis in terms of deaths was not as great, whereas the tsunami was a major, major disaster. But it very quickly fell off the screen, and all attention got focussed on Fukushima. So more a matter of newsworthy attention. That’s just the nature of the news reporting cycle, which is focused on matters that keeps attention of people, so the nuclear crisis was more newsworthy over a sustained period.
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On emergency management:

**Ali Asgary
Associate Professor of Disaster and Emergency Management, York University
More information on Ali Asgary

How prepared was Japan for a disaster like this?

Japan has experienced considerable number of large disaster events in the past. Earthquakes or tsunamis are not new to them and Japanese are normally prepared for such events. What Japanese were less prepared for was a worst-case scenario like this that combined earthquake, tsunamis and nuclear accident.  This compound disaster made emergency response and recovery very complicated and more challenging even for experienced societies like Japan. If emergency managers, officials, and general public want to know what a worst case scenario looks like and how prepared they are for such a case, they can look at Japan and see how they could have dealt with it, had it happened in their country.

There were many lessons for Japans as well as other countries.  The first and foremost is that some of our assumptions about the probability and likelihood of large events must be changed. Our industrial safety and risk assessment, and our preparedness plans need to be revised as these assumptions change.

In my view what would be useful for other countries to learn would be to always consider the worst-case scenario. When I compare Fukushima with the [Deepwater Horizon incident in] the Gulf of Mexico, it was a very catastrophic event, but not still the worst-case scenario. If it had happened during the hurricane season, that would have made this even worse. Japan’s disaster was very close to what you can call it a worst case scenario.

The time has passed for thinking and planning for simple, single disasters in limited geographic areas. We need to shift our planning focus to worst-case scenarios like the Tohoku earthquake and Tsunami. We know how to deal with typical emergencies. We need to learn more about managing large compound disasters.

This disaster showed us that we should think of worst-case scenarios. We should change our current hazard assessment methods to include secondary hazards, we should include hazards and scenarios like this in our long term industrial projects.  We should focus on the international economic and trade impacts of disasters in integrated global economy and try to mitigate such impacts.

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Useful links:

Information on an International Expert Symposium in Fukushima held last September:

http://www.nippon-foundation.or.jp/eng/media/news/2011/20111114.html

Stream of the symposium (which was followed by a large scale press conference):

http://www.ustream.tv/recorded/17194336

Published conclusions and recommendations:

http://iopscience.iop.org/0952-4746/31/4/E02

The March issue of Journal of Radiological Protection will have (as short papers) most of the presentations, available soon:

http://iopscience.iop.org/0952-4746/page/Forthcoming%20articles#Notes:_SelFukushima_

You can read more detailed reporting of the trial below.

Nature News: Scientists on trial: At fault?

BBC News: Italy scientists face trial over L’Aquila earthquake

Following the announcement of the trial in May, Italy’s National Institute of Geophysics and Volcanology (INGV) published a letter of support for the scientists. This has been signed by over 5000 researchers worldwide, including 77 Australians.

The final paragraph of the letter states:

“The scientific community involved in earthquake science urges the Italian government, local authorities and decision makers in general, to be proactive in establishing and carrying out local and national programs to support earthquake preparedness and risk mitigation rather than prosecuting scientists for failing to do something they cannot do yet – predict earthquakes.”

Below is a reaction from an Australian scientist and some comments collected by our colleagues at the New Zealand Science Media Centre.

Feel free to use these quotes in your stories.  Any further comments will be posted here. If you would like to speak to an expert, please don’t hesitate to contact us on (08) 7120 8666 or by email.

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Professor Paul Somerville is Deputy Director of Risk Frontiers at the Macquarie University

“On April 6, 2009, a magnitude 6.3 earthquake killed 308 people in the Italian city of L’Aquila, following an earthquake swarm that had produced earthquakes daily for four months. The case against the scientists was initially understood as relating to their failure to predict the earthquake (an error of omission), but is now focused on their having provided “incomplete, imprecise and contradictory information” about earthquake risk (an error of commission).

Specifically, the local government’s prosecution argument is that the reassuring information the scientists provided at a meeting held one week before the earthquake, to the effect that a major earthquake was not imminent, inhibited the citizens from taking precautions that would have saved lives, especially as two large foreshocks occurred the day before the early morning mainshock.

It appears that the government’s objective in holding the meeting was to debunk unreliable but alarming earthquake predictions that were being made by L’Aquila resident Giampaolo Giuliani, who is not a seismologist, and that the scientists were distracted in this direction instead of focusing on information about earthquake risk that the citizens needed. Further, it appears that the scientists found themselves answering questions about deterministic prediction of earthquakes (which they acknowledge is not currently possible) instead of probabilistic forecasting of earthquakes (which they can do).

However, probabilistic forecasting has very low absolute probabilities, even when the increase in probability is high. For example, Italian seismologists estimated that the probability of a large earthquake in the next three days increased from 1 in 200,000 before the earthquake swarm began to 1 in 1,000 following the two large foreshocks of L’Aquila earthquake.

Such low probabilities make it difficult for scientists to place a large degree of importance on their forecasts. Scientific errors made by members of the Commission exacerbated the situation. Dr De Bernardinis, who is an expert in floods, not earthquakes, incorrectly stated that the numerous earthquakes of the swarm were releasing stress and thereby inhibiting the occurrence of a larger earthquake.  Dr Calvi, who is a structural engineer, misunderstood the seismologists as thinking that the earthquake swarm had no impact on the likelihood of a larger earthquake; in fact the probability was estimated by the scientists to be several hundred times higher, as we have seen.

Ironically, the prosecution of the scientists, especially if it is successful, is likely to imperil the very need that this incident has highlighted: for open and clear communication between the scientists and the public. In a further irony, no action has yet been taken against the engineers who designed modern buildings that collapsed and caused fatalities, or the government officials who were responsible for enforcing building code compliance. It has occurred to some observers that the local government officials may be scapegoating the scientists to avoid prosecution themselves.

(This summary builds on excellent articles in Nature Vol. 477 p. 265, 15 September 2011 and The Economist, 17-23  September 2011 p. 86-87.)”

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The comments below were collected by our friends at the New Zealand Science Media Centre:

The comments below reflect the views of the researchers and do not necessarily represent the opinions of their organisations.

Dr Mark Quigley is Senior Lecturer in Active Tectonics and Geomorphology at the University of Canterbury

“Italian seismologists are being prosecuted for failing to provide sufficient warning of the risk of a major earthquake prior to the 2009 L’Aquila Mw 5.9 event. Specifically, the prosecution claims that scientists provided authorities and the public with “generic, ineffective, incomplete, imprecise, and contradictory information about the nature, causes, and future developments of the seismic hazards in question”. This was compounded by the fact that the mainshock followed 3 months of smaller earthquakes that were reclassified as ‘foreshocks’ following the Mw 5.9 event.”

“A survey of major earthquakes in Italy spanning the last 60 years indicates that only 6 of 26 have been preceded by foreshocks …within 10 km and 3 days of the mainshocks. As foreshocks do not appear to have any different characteristics from isolated ‘background’ earthquakes characteristic of regional seismicity, they cannot be used as diagnostic precursors to major quakes.

“So while one could say that the chance of a major earthquake increases during a seismic swarm, history dictates that more often than not major earthquakes do not follow these events, and probability of delivering a ‘false alarm’ and causing undue panic would have been quite high.

“To me this highlights the importance of effective science communication; while it is important to provide the public with probabilistic earthquake ‘forecasts’ it is equally important to contextualize these assessments (e.g., earthquake probabilities in the midst of an aftershock sequence compared to ‘background’ probabilities) and to provide sufficient information on the methodology and limitations of these forecasts.

“And finally, it is important to emphasize to the public that no precursory phenomena (e.g., gas release, micro-earthquakes, thermal anomalies, animal behavior, strain rate changes, electrical phenomena, lunar phenomena) have produced a successful and reproducible short-term earthquake prediction scheme. This is not for lack of trying, and these methods should continue to undergo scientific testing and scrutiny. However, the holy grail of earthquake prediction, as defined through specification of a defined geographic region, depth, time window, and magnitude range, remains elusive at present.”

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Dr David Rhoades is  Principal Scientist & Geophysical Statistician at GNS Science

“I signed the letter because I felt strongly that it is unjust to prosecute scientists for failing to predict an event that was unpredictable by any scientific method. In my opinion, the most scientists can do is to estimate the probability of an earthquake occurring in a given space-time-magnitude window. Giving any kind of warning, or advice to the public of what to do in the light of such information, is the proper responsibility of government authorities, and not of their scientific advisors.”

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Professor Martha Savage is Professor of Geophysics at Victoria University of Wellington

“I think that the incident shows that there is a big gap between what scientists can deliver and what the local population and politicians want us to be able to deliver. It is also not helped by non-scientists who claim to “predict” earthquakes.  It is quite difficult to know what to tell people when there is an earthquake.

“My own research has shown that in general in New Zealand, when a moderate earthquake occurs (that is not already part of an aftershock sequence), there is about a one-in-twenty possibility that another one of the same size or larger will happen within the next few days. That possibility gets lower quickly and the likelihood of big earthquakes is still small (less than 1 in 100 that an earthquake a whole magnitude larger will happen in that same time period). Yet the possibility of a big earthquake is quite a lot (100s to 1000 times higher depending on how you count it) than it was just before the earthquake.

“I usually try to communicate this to people who are concerned, and I also tell them that they should use such earthquakes as warnings to check their earthquake supplies and be sure their house is earthquake-proof. When I present the statistics as one in 20 chance of a bigger earthquake, people usually think that a one-in-twenty chance is small, and they stop worrying. But if I tell them the chance has increased more than 100 times, they will worry. Thus I can report the same information in a way that can worry or reassure people.

“I had a few people tell me after the September Darfield earthquake that I should have given people more reassurance – that they didn’t want to hear about further risks, they wanted to feel safe. Certainly after the February earthquakes I was happy that I didn’t respond to that pressure.

“Apparently one of the non-scientists attending the meeting in L’Aquila, Italy falsely stated to the population that moderate earthquakes decrease the risk of big events. I think he was responding to similar pressures. And 99 times out of 100, no large earthquake would follow the small ones. I think that he was incorrect but he may also have believed it himself – people want to believe that things will get better. So he was wrong, but I don’t think that his behaviour was criminal in any sense of the word.

“There have in fact been a couple of studies of the L’Aquila earthquake that suggest that the large foreshock may in fact have changed the fluid pressure just before the mainshock and perhaps if similar studies could be done in enough other earthquake sequences one might be able to use such studies to help to decide which future earthquakes can be triggers for larger ones. But such work is only in its infancy.”

To what degree should scientists be held accountable for their announcements regarding natural hazard risks?

“If the public decides to make scientists accountable through fines or jail terms for their announcements regarding natural hazard risks, the scientists will respond by not saying  anything, and possibly by moving their research into areas where they are not as likely to encounter such uncertainty. Therefore, the public will lose out. “

Have the Canterbury earthquakes changed the way the public view scientific information regarding risk?

“I still find people telling me that their friends are very worried every time Ken Ring makes a prediction, even though all scientists I know of discount his views.

“I think the insurance companies are rightly judging that there is still a risk of earthquakes in the region. Their money is at stake and they are likely to err on the side of caution.

“GNS Science is in my opinion doing state of the art work to assess the current probabilities of new earthquakes in the region and yet nobody can predict exact times and magnitudes.”

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Professor Euan G C Smith is Professor of Geophysics at Victoria University of Wellington

“It appears that the indicted scientists are being blamed for the lack of preparation by the community for the event that happened. That is unjust.

“In 1987 I was involved in a situation with some similarities.

“In February 1987 I was acting superintendent of the Seismological Observatory, DSIR, when an earthquake swarm started (Feb 21) near Maketu in the central Bay of Plenty. After a few days of activity, my Director thought we should say something about the earthquakes. Accordingly I issued a press statement on March 2 saying that there was no reason to expect that the earthquakes would lead to a bigger one (such swarms are common there) BUT that earthquakes were likely to be ongoing and residents should take sensible precautions.

“While this was being aired by the media, the Edgecumbe earthquake (mag 6.5) struck at 1.42 pm. I was somewhat derided in the media – the Auckland Star sent me an electric kettle for getting into hot water. It might have been much worse for me if there had been heavy casualties, but there weren’t. Of course, no-one wanted to read the disclaimer (‘BUT…’) And so the main lesson that I took from these events is that extreme caution is required in such circumstances. I thought I had covered off the possibility of something larger happening, but the media didn’t.

“In similar circumstances I would make a statement again, albeit with the benefits of this (and other) experience. The public are entitled to expect that experts will give them an opinion. If we (scientists) have not adequately explained that the future is uncertain and that, in particular, earthquakes cannot be predicted deterministically, then that’s our fault.

To what degree should scientists be held accountable for their announcements regarding natural hazard risks?

“I was accountable for the statement I made at the time, and would expect to be in future. I note that Mr Ring is not accountable for his statements.”

Have the Canterbury earthquakes changed the way the public view scientific information regarding risk?

1. Many more people in New Zealand now understand that earthquakes can only be ‘predicted’ probabilisitically.
2. At least one centre – Wellington – has been galvanised into action over its stock of earthquake-prone buildings, and there appears to be widespread acceptance, in Wellington at least, that civic preparation against earthquakes is essential even if it means some loss of ‘heritage’.”

Feel free to use these quotes in your stories.  Any further comments will be posted here. If you would like to speak to an expert, please don’t hesitate to contact us on (08) 7120 8666 or by email.

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Dr Gary Gibson is Principal Research Fellow in the School of Earth Sciences, University of Melbourne

“Korumburra is located about 100 km southeast of Melbourne, in the Strzelecki Ranges of South Gippsland. These ranges extend from Westernport Bay in the west, south of the Latrobe Valley, and towards Sale.

This part of Victoria is being compressed from southeast to northwest, largely as a result of movement between the Pacific Plate and the Australian Plate in the New Zealand region. It results in a number of faults that run from southwest to northeast.

The Strzelecki Ranges have been uplifted by hundreds of metres over the past 10 million years, or tens of metres per million years. This is a relatively high rate of fault movement for a stable continental area, but much less than the relative movement at active tectonic plate boundaries, which can reach tens of kilometres per million years.

Over the past hundred years the western part of the Strzelecki Ranges, around Korumburra, has experienced fewer earthquakes than the region south of the Latrobe Valley. On 12 January 2009 a magnitude 3.7 earthquake occurred just northeast of Korumburra, and was followed by a magnitude 4.7 on 6 March 2009 and another magnitude 4.7 on 18 March 2009, both felt in Melbourne.

A total of over 300 small earthquakes have occurred at the same place over the last couple of years. All of these were located about 4 kilometres northeast of Korumburra, at a depth of about 8 kilometres beneath the surface. Because of the depth and moderate to small magnitudes, none have caused any damage, but many of the smaller earthquakes have been felt locally. Additional seismographs have been installed in the area by the Seismology Research Centre at ES&S to monitor the smaller earthquakes.

At 11:32 am on Tuesday 5 July 2011, another earthquake of magnitude 4.4 occurred at the same place, and was felt in Melbourne. It was followed by four aftershocks in the next hour, up to magnitude 3.1.

Single clusters of earthquakes of this size are not unusual in Victoria. An earthquake of magnitude 4.1 occurred in the Grampians, northeast of Dunkeld and about 210 km west of Melbourne on 1 June 2011. However a series of earthquakes lasting over two years is unusual. It is very likely that more aftershocks will occur in the current cluster over the next few days, and that more clusters may occur in the next few months. It is possible that one of these clusters may include an earthquake larger than today’s event. As with any earthquake, it is not possible to predict what will happen with any certainty.”