宇治田原及び和束盆地における微動を用いた地盤構造調査

Abstract

Microtremor measurements were conducted in the Ujitawara and Wazuka basins, southern part of Kyoto Prefecture. The H/V spectra were obtained at 42 sites in Ujitawara and 37 sites in Wazuka. The peak frequency of H/V spectra was 0.9-1.4 Hz at sites in the western part of the Ujitawara Basin, whereas it was high (7-10 Hz) in the Iwayama area, the eastern part of the basin. The H/V peak frequency was high (2.5-16 Hz) in the valley bottom lowland along the Wazuka River. It was 1.0-2.3 Hz in hills of the Osaka Group, and it indicates that the thickness of sediments deepens towards the Wazukadani Fault. The estimated bedrock depth by the microtremor array survey was 165 m in the western part of the Ujitawara Basin. Small-sized microtremor array surveys were also conducted in the Ujitawara and Wazuka basins. The estimated phase velocities were relatively high, suggesting that the alluvium low-velocity sediments are thin in these two basins.