岡山平野児島湾岸部での微動アレイ探査

　This report describes microtremor array observations conducted at two sites for deep exploration and three sites for shallow exploration around Kojima Bay area in the southern Okayama Plain. Based on these records, the ground velocity structures were estimated. The results yielded solutions indicating the depth of the top of the seismic base layer (equivalent to 3 km/s layer) ranges from 140 to 300 m, while the depth of the top of the engineering basement layer (equivalent to 0.6 km/s layer) is approximately about 13–14 m. The shallow exploration results also suggested the possible presence of an inversion layer. These estimated velocity structure models provided a reasonable explanation for the observed phase velocities.