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EARTHQUAKES

Japan quake - no relation to Christchurch
Saturday 12 March 2011, 11:28AM
By Science Media Centre
494 views


Japan is dealing with a damaged nuclear reactor, widespread fires and the impact of a devastating tsunami in the wake of the 8.8M earthquake that struck the country last night.

Contact the SMC if you are looking for local experts to comment on the earthquake. The UK Science Media Centre has an extensive Q&A with scientists on aspects of the earthquake and tsunami here.

The Science Media Centre of Canada has also created a backgrounder on tsunamis which can be downloaded here.

See below for comment on the impact on Japan's nuclear reactors, the lack of a link to the Christchurch earthquake, the unfounded supermoon theory and the size of the quake relative to previous events.


Resources on the earthquake and tsunami:

NERC information on the quake.


British Geological Survey alerts:

Honshu earthquake


Japan earthquake special


Japan Meteorological Agency tsunami info


Is there any relation to Christchurch earthquake?

Prof. Dr. Polat Gülkan, President of the IAEE (International Association for Earthquake Engineering) and a member of the Editorial Board for Earthquake Engineering and Structural Dynamics, says:

"In terms of causality, none. They are both on the same so called Pacific Ring of Fire belt but are so far from one another that it's a very remote possibility that one triggered the other. The Christ Church event was M6.3, so this M8.9 one packed about 8,000times more energy but was much further removed from any urban area, so its effects in terms of ground shaking were milder. The tsunami waves are really one way of transporting the energy released by the earthquake to points farther."

Dr John Elliott, Department of Earth Sciences, University of Oxford, says:

"There is no relation to the Christchurch earthquake - these earthquakes were 'relatively' small and a long way away."

Dr David Rothery, Open University, Volcano Dynamics Group, says:

"No".

Dr Lisa McNeil, senior lecturer in geology at the University of Southampton, says:

"No. Earthquakes happen regularly on active faults around the world, so it is not surprising to have a magnitude 6.3 earthquake (in New Zealand) followed several weeks later by a magnitude 8-9 earthquake somewhere else."

Prof. George Helffrich, University of Bristol Earth Sciences says:

"No. Most earthquakes happen on plate boundaries. Both the Christchurch and the Japan earthquakes did, too."

Dr Alex Densmore, Department of Geography and Institute of Hazard, Risk and Resilience, Durham University, said:

"There is not likely to be any direct connection between today's earthquake and the recent Christchurch earthquake. They occurred many thousands of km apart, on different plate boundaries. There is, on average, one large (magnitude 8.0 or greater) earthquake in the world each year, and Japan has a long history of large earthquakes, so this is not unusual. It is likely to be, however, the largest recorded earthquake (in terms of magnitude) since historical records began with the 684 earthquake off Tokyo.

Paul Haigh, a Fellow of the Institution of Chemical Engineers (IChemE) and an independent nuclear consultant said:

"All Japanese reactors are designed to withstand substantial earthquakes since they are situated in a known earthquake zone. Instrumentation is provided for the early detection of tremors which would lead to a controlled shutdown of the reactor. These systems appear to have successfully shut down the affected reactors. Problems at Onagawa are attributed to the failure of mechanical/electrical systems used to provide cooling water.

"Several years ago a power reactor in Armenia was closed down as it was in an earthquake zone. After several years, with EU assistance, the reactor was upgraded, including substantial 'seismic proofing' and the reactor was returned to service. Modern western reactors, including those planned for the UK, are already designed to withstand significant seismic events. Tremors have been detected at UK power plant in the past.

"It is to be hoped that the Japanese reactors will not have suffered damage which precludes their return to service, but that is a matter for the Japanese utility and licensing authorities."

Dame Sue Ion, nuclear engineer and Fellow of the Royal Academy of Engineering, said:

"Japan has extremely tight standards when it comes to earthquake resistance of nuclear power plants and other facilities. Authorities and utilities and reactor vendors ensure that appropriate safety systems are incorporated at the design stage and implemented in construction and operation. Systems automatically shut down when trigger points are reached to allow for relevant saftey inspections to take place before restart. Japan's nuclear power stations are being shown to be robust against the threat of earthquake: Safety systems have operated as they should. Authorities have well developed precautionary evacuation procedures pending confirmation of ongoing safe operations.

"Although this earthquake is particularly severe, the devastation we are witnessing on our TV's is mainly associated with the subsequent Tsunami not the quake itself."

Dr. Clark H. Fenton, Senior Lecturer in Engineering Geology & Seismic Hazards, Imperial College London, said:

"The Japanese nuclear power plants will be designed to withstand very large earthquake such as today's event. The major radiation containment systems (reactor core, etc) are very well designed and are usually not vulnerable to seismic shaking. The nuclear power plants will be fitted with detectors that register earthquake ground motions; once these register shaking above a threshold level they will activate systems that will automatically bring the plant to an immediate and safe shutdown. Where problems have arisen in the past are with peripheral systems (electrical power, fire suppression systems, etc.).

"In 2007 a M 6.6 earthquake caused damage at the Kashiwazaki-Kariwa power plant. This relatively small earthquake caused numerous problems at the site - from radioactive water leaks to cracked cooling pipes. Most of these problems have been addressed and the lesson have been learned and action taken to prevent further such damage. Having said that, this is a truly massive earthquake and the levels of ground shaking experienced may be large enough to cause damage the more fragile elements of the plant.

"I believe from the news reports that at least one nuclear plant (Fukushima Daiichi, north of Tokyo) suffered damage to its cooling water system but there has been no release of radioactivity. Even after shut down nuclear plants still need water for cooling purposes, so continued loss of the cooling system would be a major concern. I would imagine that the surrounding region will be evacuated as a precaution if this is the case.

"There is also a report of a fire at one plant that has since been extinguished, again with no report of radioactivity release. I do not know which plant this report refers to.

"As most nuclear power plants are located along the coast, they are vulnerable to the impact of tsunamis. The actual impact will be a function of wave height and the elevation of the plant above sea level (obviously!). Such coastal sites normally have berms or sea walls to deflect storm surges and other anomalously high waves."

From the Science Media Centre of Canada:

John Luxat, Professor and Industrial Research Chair in Nuclear Safety Analysis, McMaster University

What seems to have happened at the Fukushima nuclear plant?

"It's very difficult to make definite conclusions at this point because information is coming in bits and pieces. What we do know is that when the quake hit the reactors at Fukushima, there were three of the reactors up and running - the other three were shut down for regular inspection. The three that were up and running immediately shut down, as they are designed to do when the ground shakes above a certain level.

"The emergency backup diesel generators that provides electricity to the shutdown cooling system operated as designed for about an hour, and then they failed for some reason that's not clear. They lost power to the pumps providing cooling water. Reports are that they have brought in backup generators and hooked them up.

"One reactor is reported to have a slightly greater problem with cooling, which is not fully clear.

"At this stage, they need to reestablish the electrical power supply to the cooling system.

"The other thing is that the containment buildings haven't suffered any reported damage. The plants are designed to strict seismic requirements because they're in an earthquake region in Japan, and there's no reported damage to these structures. The function of a containment building is to contain any radioactive material released from the reactor and limit any subsequent release outside the plant."

What sort of timeline is there in getting the cooling system running? How long do they have?

"I hesitate to give a direct answer because information is still very sketchy. It would be many hours. It helps that it doesn't appear any pipes were ruptured. If you don't get water in, it's a bit like boiling a kettle dry...it takes awhile.

"Once power is restored, you just need to get the water up to a safe level. After that, it's relatively quick to reestablish cooling.

"To monitor, they will be measuring water levels, and temperature and pressure as well - a number of parameters. And some steam might be expelled from the reactor into the containment building. If they release steam from the containment unit, it's called venting. That's a preventative measure to reduce pressure in the containment building.

"You would normally have some levels of radioactivity in the coolant, this would not be a major safety issue. It would be gas released with the steam, a mixture of things like xenon, krypton - some short-lived and some longer-lived. Any release of radioactive gases at this stage would be very small compared to, say, Three Mile Island, and the impact of those gases outside the Three Mile Island plant was as close to zero as you can get.

"Once they stabilize the reactors, they won't be able to restart until they've done detailed inspections. Inspectors and regulators from Japan and the international community will be involved, including the International Atomic Energy Agency. They will need the approval of Japanese regulators who will likely seek concurrence from experts in the international community."

Will there be any effects on the national power supply?

"It's not going to be that big an effect - the three reactors that were operating at this site are smaller than the average and don't have a huge generating capacity."

Is there anything else that should be mentioned?

"This is very, very different from Chernobyl. It's not a comparable situation - they didn't have a containment unit, and the reactor didn't shutdown prior to damage occurring, as was the case here.

"There is a desire to frame this as a nuclear disaster story - but there's been far more significant damage to the petrochemical industry, and the country's infrastructure from the earthquake and resultant tsunami. The nuclear infrastructure is built to very high standards, it may be the most robust in that country."

On the magnitude of the earthquake and the resulting tsunami:

Prof Dave Tappin, Marine geologist and expert in tsunamis, British Geological Survey, said:
"You need an earthquake of larger than 7 to produce a dangerous tsunami, this one was 8.9. This tsunami will travel around the world, the Indian Ocean earthquake of 2004 which was 9.3 sent a tsunami around the world 3 times. It's unlikely that there will be tsunami associated with the aftershocks as you need an earthquake of above 7, the aftershocks have been 7 and below. The effects of the tsunami will be measured here in the UK by tide gauges."

Dr Roger Musson, Head of Seismic Hazard, British Geological Survey, said:

"This is the sixth largest earthquake that's ever been recorded since seismographic records began in 1900. It's certainly the largest earthquake to have affected Japan in the last century and considerably larger than anything else in living memory in Japan.

"The largest previously was the 1923 Canto earthquake, the one that caused so much damage in Tokyo, that was only 7.9. That's 30 times less powerful than this one."

Dr Jeff Peakall, Reader in Sedimentology at the University of Leeds, said:

"The only real to defence against the largest tsunami events like this is by optimising the coastal zone, and the best way to do this is by planting trees. For example, a 10m high wave will travel almost 6km inland over developed coastal areas, whereas if that area is covered in forest it will travel just 260m.

"Hard engineering with sensors, walls and other defences works against smaller events, but this soft engineering with forest is more practical against large events, particularly on flat land where the option of running uphill is not readily available."

On the "supermoon" theory:

Dr Alex Densmore, Department of Geography and Institute of Hazard, Risk and Resilience, Durham University, said:

"There's absolutely nothing whatsoever to the 'supermoon' theory. There are about 150 earthquakes per year that are large enough to cause significant damage - that is, with a magnitude greater than 6.0. This means that there is on average about one every other day, irrespective of where the moon is. In other words, there is always an earthquake that can be attributed to an external cause (like a close approach of the moon), no matter when or where that cause occurs."

John S Whalley, Geoscience Programme Manager, University of Portsmouth, said:

"There is no established correlation between variations in the orbit of the moon and either the number or magnitude of earthquakes. It is all too easy, with hindsight, to link major earthquakes to variations in all sort of parameters. The real test is to look at the vast numbers of earthquakes of all magnitudes that occur on a daily basis worldwide. 






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