A new panel of experts convened by the Tokyo metropolitan government now estimates up to 10,000 deaths if a major quake struck directly under the capital.
An estimate made six years ago had about 6,400 fatalities. The revision is due to forecasts that much of the 23 wards in the Tokyo area would be hit by shaking of at least an upper 6 on the Japanese "shindo" (seismic intensity) scale of 7, which reflects the degree of shaking on the ground. That is expected to lead to the collapse of buildings and fires that would increase the number of fatalities.
The new estimate is based on the findings in March of a science ministry research team on the subterranean structure of the Tokyo metropolitan area. It will be included in new damage calculations to be released by the Tokyo metropolitan government on April 18.
"It will be important that the estimate serves as a stimulus for thinking about what preparations should be made for an earthquake," said one researcher who was part of the panel that made the new calculations.
The disaster management panel, comprised of experts and established by the Tokyo metropolitan government, made the estimates based on an assumption of a magnitude 7.3 quake with a focus in the northern part of Tokyo Bay. Another assumption used by the panel was the quake striking at 6 p.m. on a winter day when the likelihood of damage from fires would increase because humidity would be low and the winds would be strong.
In March, a research team of the science ministry released a new intensity distribution map for a quake striking directly under Tokyo. That team used a new finding of a plate boundary capable of generating earthquakes that was around 10 kilometers closer to the surface in some places than previously assumed. A shallower epicenter usually increases the intensity of shaking on the ground.
The Tokyo metropolitan government's panel also used that new finding in place of assumptions used in calculating the estimates six years ago. Using the new assumptions led to new locations in the capital that would likely suffer shaking with a maximum 7 on the shindo scale.
In the research done six years ago, estimates of the degree to which buildings would not catch fire were made by units of neighborhoods. This time, more accurate figures were calculated by using figures compiled by ward and municipal governments on the degree to which individual buildings would likely catch fire as well as the degree of building density in each neighborhood.
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