2015 Volume 15 Issue 7 Pages 7_194-7_204
Microtremor array observations and single-station microtremor observations are conducted in the Kaga plain and the Ochigata plain, Ishikawa prefecture, Japan, to improve the three-dimensional velocity structure model for strong motion prediction in this area. The lateral variation of the peak periods estimated from the H/V spectra and phase velocity estimated from the array observation are discussed in terms of three-dimensional structure of subsurface sediment layers and bedrock depth. The peak period is relatively short around Komatsu city in the southern part of the Kaga plain compared to the northern and central part of the Kaga plain, indicating the change in the bedrock depth or thickness of sediment layers, which is not well considered in the present velocity structure models. In the Ochigata plain, our observations indicate the need for improving the present model to explain that the thickness of sediment layers gradually increases along the observation line from northeast to southwest.