Estimation of Seismic Hazard in Hikone City Based on Observation Network Data from Shiga Prefecture, Japan

Abstract

The seismic observation network in Shiga prefecture is composed of four systems. All the observation data obtained were used to estimate the dynamic characteristics of the surface soils around the lake and the seismic hazard for Hikone City. Since 1995, 21 records have been obtained at the USP site of which those for the 1999 Shigaken-Hokubu Earthquake and 1999 Wakayamaken-Hokubu Earthquake were used in this study. Transfer functions of the surface soil in each ward of Shiga Prefecture based on the Mt. Kojin site (KJY), which has relatively hard soil, were calculated from the records of the two earthquakes. Assuming a scenario earthquake at the Hyakusaiji fault close to Hikone City, maximum ground motions were obtained for 15 city blocks in order to establish a damage estimation for that city. The number of collapsed wooden houses and the damage ratio were calculated based on the distribution of construction of wooden houses by year. Blocks with a larger ratio of old, wooden houses in Hikone showed a close correlation with blocks with a large ratio of aged persons in them, indicative that weak persons, such as the elderly, may find themselves in a severe situation during a natural disaster.