SEGJ Technical Conference

Estimation of S-wave velocity structures in the creation land of central Rikuzentakata City, Iwate Prefecture by using dense microtremor array surveys

Abstract Microtremor observations with arrays of a radius of 60 cm and with arrays of a distance of a road width were carried out densely in the Takada area of Rikuzen-Takata City. The S-wave velocity structures were estimated by using the observed phase velocities and H/V spectral ratios. The S-wave velocities at a shallow part were estimated to be 200 - 350 m/s, and the depths of the basement with an S-wave velocity of about 800 m/s were estimated to be 30 - 50m. In addition, at some points where the observed phase velocity could not be fitted to the fundamental phase velocity, the observed one cloud be fitted to the effective phase velocity including the multiple modes of the surface wave. It was found that the layer model considered in all modes showed a shallower basement than the model estimated by only the fundamental mode.