While the seismic resistance of buildings and houses in Tokyo has improved in recent years, some of the capital's eastern areas remain particularly susceptible to building collapse and fire in the event of a massive quake, according to a new Tokyo Metropolitan Government report, cited in the Japan Times.
Vulnerable wards with poorer infrastructure
Researchers at the central government-run Headquarters for Earthquake Research Promotion predict that the risk of Tokyo being hit by an earthquake of magnitude 7 or above within the next 30 years is as high as 70%.
In its assessment on Tokyo’s disaster risks issued last week, a process conducted about every five years since 1975, the metropolitan government highlighted some communities as being particularly at risk—notably those where old wooden houses and light-gauge steel buildings are concentrated.
Some of these wards at highest risk are southern Adachi and Arakawa, western Katsushika and northern parts of Sumida and Koto. Areas along the JR Chuo Line and Tokyo Metropolitan Road Route 318, also known as Kannana Dori, too remain susceptible to fires due to a concentration of wooden residences.
The report said that the poor infrastructure in those regions — which are located mostly in alluvial and valley lowlands along Arakawa and Sumida rivers — would also hinder emergency responses if a megaquake hits and that the soft, soil-based ground would amplify the shaking, noted the Japan times.
Adachi, Sumida and Arakawa wards also topped the list of areas most susceptible to damage from fires, according to the report.
The metropolitan government also noted that rescue efforts in areas with poorly established road networks and a high concentration of wooden buildings may be unsuccessful following a massive quake. Poor road conditions near the No. 7 loop road, residents of Nakano and Suginami wards, as well as a large portion of the city of Tama in western Tokyo, may face serious challenges in a disaster as help in those areas may not arrive on time, the report said.
Levels of risk are also assessed as relatively high in southwestern Shinagawa Ward, central Ota Ward, northern Kita and Toshima wards, Nakano Ward and western Suginami Ward.
Improvement over the years
Despite the risks, the assessment was that the overall risk of building collapse has decreased by about 20% over the past five years, while fire hazard risk has dropped about 40%, reported the Japan Times.
The metropolitan government examined 5,177 communities in Tokyo to check for vulnerabilities in the event of a potential earthquake, looking at factors including the ground beneath the buildings, the space between them, and their age and structural type. The fire threat factored in not just the risk of fire outbreak but also the risk of it spreading.
In the lead-up to the 2020 Tokyo Olympics and Paralympics, Gov. Yuriko Koike has prioritised upgrades to seismic measures in the capital. By 2019 Tokyo plans to raise the proportion of quake-proof structures to around 90%, while the authorities aim to ensure 100% quake-resilience by 2025.