Author(s)

Harumi Yashiro & Takayuki Hayashin

Abstract

It is estimated that Japan’s population will peak in 2008 and decline thereafter. The urban structure is expected to change significantly due to this population decline. Kkanagawa prefecture in Japan, which is the target of this study, occupies a part of the Tokyo metropolitan area, and estimates have been published that show a decline in population from 2020. In response to such a future population decline, plans are being made for a compact city with the aim of optimizing the population distribution. On the other hand, Japan is a country with high potential for many natural disaster risks. In particular, the Tokyo metropolitan area has a high probability of earthquake occurrence and is an area with high earthquake risk.

We analyse the change of earthquake risk due to the future population decline and the change of earthquake risk by inducing a compact city utilizing population decline. In Kanagawa prefecture in the metropolitan area of Japan, we analysed the forecast of the decrease in residential buildings due to population decline by structure, building age and building height. The seismic damage evaluation was carried out using the same three earthquake scenarios as the seismic damage assumed by Kanagawa prefecture. The number of damaged buildings in the future was calculated for each earthquake scenario. The earthquake scenarios are 1) tshin nanbu earthquake, 2) miura peninsula fault group earthquake and 3) kanto earthquake. Building damage is estimated every 10 years from 2020 to 2040 due to population decline in each scenario. Next, we analyse the change in earthquake risk caused by the compact city policy due to population decline and other disaster prevention measures.

In this study, we examined the change of the earthquake risk by the compact city plan according to the future population decrease in Kanagawa prefecture.

Keywords

Earthquake risk, future population, number of damaged buildings, compact city, Location optimization plan.