堆積平野の基盤構造推定における微動アレイ探査法の適用限界の検証

Abstract

Since the Great Hanshin Earthquake of 1995 in Kobe, the importance of the basement structure and its influence to strong motion characteristics on surface of sedimentary plain have been discussed. In order to clarify deep structure of the Nohbi Plain and the Toyohashi Plain, reflection survey and microtremor array measurement had been performed from 2001 to 2004 by the Aichi Prefecture Office. However, in some cases, the structures estimated by two methods do not conformed. It means that microtremor array method will have the limit of surveying in a particular structure of sediments. In this paper, microtremore array measurements were carried out in the Nohbi and Toyohashi Plain paying scrupulous attention to the sensors, devices, array size, traffic noise, so on. In Nohbi Plain, the structures obtained by array survey well conformed. However, in the Toyohashi Plain, the depth of the basement estimated by array method is shallower than that by reflection method. It is considered that the higher mode of Rayleigh wave will be measured because of particular structure of the Toyohashi Plain. It is concluded that array method has the application limit for surveying deep structure of basement.