[S-SS11] Strong Ground Motion and Earthquake Disaster

[SSS11-P09] Microtremor characteristics and subsurface structure in the vicinity of the Shikano-Yoshioka Fault, Tottori, Japan

*Tatsuya Noguchi¹, Kazuki Kobayashi², Ryo Ashida¹, Isamu Nishimura³, Takao Kagawa¹ (1.Faculty of Engineering, Tottori University, 2.Graduate School of Sustainability Science, Tottori University, 3.Graduate School of Engineering, Tottori University)

Keywords:Shikano-Yoshioka Fault, Microtremor characteristics, subsurface structure

The Shikano-Yoshioka fault is an earthquake fault that appeared due to the 1943 Tottori earthquake. At both faults, trench surveys, reconnaissance surveys, and interview surveys with residents are conduct-ed as fault displacement surveys. For the ground structure, microtremor exploration and gravity exploration were carried out. In addition, dense microtremor observations were also carried out at and near the fault displacement. However, the difference in ground motion characteristics due to irregularities such as crush zones and step structures due to faults has not been sufficiently investigated.

In this study, we grasped the ground motion characteristics in the vicinity of the fault by using the results of dense microtremor observations at the fault displacement location and in the vicinity. As a result, there was a difference in the shape of the microtremor H/V, predominate periods and particle motion of records between the front and the back of the fault displacement point. As the cause of this phenomenon, the correspondence between the results of microtremor observation and underground structure exploration suggests that the crush zone and step structure of the fault are in-volved in the characteristics of microtremor.