DETERMINATION OF UNDERGROUND STRUCTURE OF IZUMO PLAIN AND MATSUE PLAIN, SHIMANE PREECTURE

Abstract

Microtremor observations and gravity surveys data were analyzed in Izumo Plain and Matsue Plain to determine the underground structures. The result is as follows. S wave velocity structure models were obtained at 4 sites from the data of microtremor array observations. 2D density structures were determined from the gravity data by using a 2D gravity analysis. From the comparison of the seismic refraction and the gravity analysis results, the depth to bedrock and the configuration were found to be almost same. The 3D model of bedrock surface was obtained by a 3D gravity analysis using the results of microtremor array observations for the depth to bedrock as control points. The depth to bedrock was found to be about 1100m at most.