Recent Seismic Microzoning Maps in Japan

Abstract

In Japan, seismic microzoning has been conducted as the basis for better disaster planning by governments. This paper introduces various seismic microzoning maps published by the central and local governments in Japan after the 1995 Kobe earthquake. Nation-wide seismic hazard maps are published by the Headquarters for Earthquake Research Promotion, to understand the general view of seismic hazard nationwide. Regional seismic microzoning maps are prepared by the Central Disaster Prevention Council for large subduction earthquakes and the Tokyo Metropolitan earthquake. Based on results of the microzonings, strategies are proposed for disaster mitigation of the earthquakes. Local governments prepare more detailed, smaller scale maps, e.g., the Yokohama shake map using a 50 m mesh system. After the publication of the map, the numbers of applicants for seismic performance appraisal service of wooden houses and for seismic retrofitting subsidies from the city increased significantly. This stimulated central and local governments, which started detailed mapping studies. Seismic microzoning maps are being used not only for governments but also for citizens. The maps should evolve both for more attractive presentation to deepen citizens' understanding and for more reliable and comprehensive estimates of seismic hazard and risk.