In order to clarify the surface ground motion characteristics at Zushi site which has irregular ground condition, horizontal and vertical array earthquake observations were performed at the five stations(K1,K2,K3,K4,and K5) on the ground surface and one bedrock (-30m depth k6) in Zushi City, in 1994. Approximately 100 earthquakes were recorded between July 1994 to December 2003, including the Chibaken-nanbu earthquake (M=5.2), for which Zushi recorded a maximum acceleration of 75 gal (horizontal component). Microtremor measurements were also performed at about 60 points on the surface and seismic explorations were conducted at two sites (K1 and K2) to examine the resonant frequency and the structure of surface ground. From these data, the soil structure and seismic characteristics of the surface ground in Zushi were clarified._A new identification analysis method to estimate the surface ground characteristics using horizontal array observation records, were developed. It is based on assumption that each incident wave of neighboring observation points in the common basement deconvoluted by the multiple reflection theory almost agrees. The soil structure and the seismic response characteristics of the surface ground were verified through the comparison of the identified results and the observed ones The identification method and the results are useful for seismic disaster mitigation and seismic design of structure in Zushi.
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