Last week, the media was filled with reports on Tokyo’s latest projections regarding what residents could expect if a major earthquake struck the capital. The parameters used for the simulation were a 7.3M quake that occurred directly beneath the prefecture’s 23 wards, with a shindo reading of 6+ for the city center, and shindo 7 for riverbank and coastal areas. It would occur in the wintertime with wind speeds of 8m/second. For the most part, the news was relatively good in that the number of deaths (6,200) and amount of damage (194,000 structures) estimated were less than in past projections—30 percent less, as a matter of fact.
In detail, 50 percent of the deaths would be caused by collapsed houses, and 40 percent the result of fires. In both cases, the houses involved would be older wooden structures that are densely concentrated, so the prefectural government has said—not for the first time—that it will work harder on providing subsidies for the rebuilding of such houses to make them less vulnerable to earthquakes.
An important factor in the lower casualty and damage numbers estimated by the report is improved quake-proofing since the last report was compiled. The portion of houses that have been quake-proofed since 2010 increased by 10.8 percent, which means 92 percent of all homes in Tokyo have some form of quake-proofing. In addition, the total area of densely packed wooden houses has decreased by 46 percent since 2012. The government now estimates that 4.53 million workers who live outside the capital would not be able to return home on the day of a major earthquake, and of the city’s residents 2.99 million would have to evacuate their homes. But while these numbers sound high, they are down by 12 percent from the last report.
However, there is one sector where matters have not improved: high-rise residential apartment buildings. As we’ve written in this blog numerous times in the past, so-called “tower mansions” have unique problems when it comes to earthquakes that have nothing really to do with their ability to withstand the tremor itself. All multi-story buildings in Japan, whether for commercial or residential use, are constructed to the world’s strictest quake-proofing standards, and are expected to maintain their integrity even during a catastrophic temblor. The problems occur after the shaking, and none have been solved in the past decade while at the same time there has been a 30 percent increase in the number of high-rise residential apartment buildings and condos during that time. At present, there are some 600 “tower mansions” in Tokyo, which are defined as multi-residence buildings that are at least 45 meters tall.Read More