A magnitude-8.0 aftershock could strike the Tokyo metropolitan area or northern Japan within a year, a seismologist warns, underscoring the fresh need for the populace to prepare for a massive temblor.
A magnitude-8.0 aftershock could strike the Tokyo metropolitan area or northern Japan within a year, a seismologist warns, underscoring the fresh need for the populace to prepare for a massive temblor.
Although Japan , one of the world's riskiest countries for earthquakes and tsunami, is supposed to be well prepared, the magnitude-9.0 quake on Friday caused widespread devastation and a rising death toll in northeastern Japan.
The Asahi Shimbun interviewed three experts about what Japan should do to improve its quake preparedness: Yasuhiro Umeda, seismologist and professor emeritus at Kyoto University; Seiichi Sakurai, representative auditor for the Kobe municipal government who led the city's publicity section and was involved in relief programs after the 1995 Great Hanshin Earthquake; and Yoshiaki Kawata, professor of disaster prevention at Kansai University and the head of Disaster Reduction and Human Renovation Institution.
Excerpts of the discussion follow:
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Question: What are the prospects for aftershocks?
Umeda: We are most concerned about the largest aftershock, whose magnitude could reach 8.0. The latest quake is believed to have caused a fault to rupture measuring 400-500 kilometers north and south and 150 km in width.
It could occur either at the north end of the fault or at the south end. If it occurs at the south end, it could strike the Tokyo metropolitan area. Under that scenario, Japan would have to grapple with a very difficult situation.
Kawata: According to records on the Ansei Nankai earthquake in 1854, aftershocks continued for as long as a year. Extra precautions are required for the coming year.
Q: Tsunami warnings were issued as early as four minutes after Friday's quake. The largest wave of the tsunami came an hour later. Why couldn't more people evacuate?
Sakurai: TV showed some people were cleaning up the damage at their homes after the quake despite the evacuation order. Concerns arose when many people did not take refuge after a large quake hit Chile in February 2010. As a public service member, I think we have to find ways to educate the public.
Kawata: In the case of the temblor in Chile, only 3.8 percent of residents in the affected area took shelter when evacuation orders and instructions were issued.
Japan was hit by the Meiji Sanriku quake in 1896 that killed 22,000, and the Showa Sanriku temblor in 1933 that left 3,064 dead or missing, but there are no mechanisms for passing along lessons from those experiences.
Q: What is the most important aspect of the relief operations?
Sakurai: It is gathering information on where and how many people have survived. Without that information, officials in charge cannot draw up a contingency plan nor know where to send rescue teams.
Kawata: Officials should devise objective yardsticks, such as determining the size of rescue operations in accordance with the different heights of the tsunami.
Q: Telephone and e-mail services did not work. What should we do in response to the disrupted communication systems?
Sakuari: Cellphone services were disrupted in Tokyo, too. Cellphones come in handy, and people tend to turn to them to contact others. But we should have knowledge or educate the public about using a message service to confirm the safety of others.
In principle, those who have difficulty returning to their homes are supposed to stay where they are as long as their safety is ensured. But after Friday's quake hit, many people tried to walk home or rent a car. The principle is not yet well understood. Businesses and others must have better ideas on what to do.
Q: Does the latest jolt indicate that the Tokai, Tonankai and Nankai earthquakes may hit simultaneously, shaking the Pacific coast of central and western Japan?
Umeda: It has been believed that those three quakes can occur in conjunction with one another.
There is no scientific ground to suppose that the latest quake could directly trigger these three quakes. Nevertheless, it is necessary to keep watch over them because there have long been concerns that the probability for their occurrence is high.