IDENTIFICATION OF SURFACE GROUND CHARACTERISTICS USINGHORIZONTAL ARREY EARTHQUAKE OBSERVATION RECORDS ANDITS APPLICATION

摘要

In order to clarify the surface ground motion characteristics at Zushi site which has irregular groundcondition, horizontal and vertical array earthquake observations were performed at the fivestations(K1,K2,K3,K4,and K5) on the ground surface and one bedrock (-30m depth k6) in Zushi City, in1994. Approximately 100 earthquakes were recorded between July 1994 to December 2003, including theChibaken-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 surfaceand seismic explorations were conducted at two sites (K1 and K2) to examine the resonant frequency andthe structure of surface ground.From these data, the soil structure and seismic characteristics of the surface ground in Zushi wereclarified._A new identification analysis method to estimate the surface ground characteristics usinghorizontal array observation records, were developed. It is based on assumption that each incident wave ofneighboring observation points in the common basement deconvoluted by the multiple reflection theoryalmost agrees.The soil structure and the seismic response characteristics of the surface ground were verified throughthe comparison of the identified results and the observed onesThe identification method and the results are useful for seismic disaster mitigation and seismic design ofstructure in Zushi.