[S-SS10] Active faults and paleoseismology

[SSS10-P04] Gravity survey around the eastern margin fault zone of the Yokote Basin, northeast Japan

*Haruo Kimura¹, Yasuhira Aoyagi¹, Motoshi Tomura², Katsuya Noda² (1.Central Research Institute of Electric Power Industry, 2.Geosys Inc.)

Keywords:eastern margin fault zone of the Yokote Basin, active fault, fault segmentation, Rikuu earthquake, gravity survey, subsurface structure

The eastern margin fault zone of the Yokote Basin, which is composed of N–S trending east-dipping active reverse faults, is divided into a northern segment and a southern segment. During the 1896 Rikuu earthquake (M_jma = 7.2), significant surface ruptures were emerged along the northern segment of the fault zone. However, no surface trail ruptured by the 1896 earthquake have been found along the southern segment. We conducted a gravity survey around the eastern margin fault zone of the Yokote Basin to reveal the subsurface structure beneath the area. Gravity anomaly maps of the study area were obtained after data analysis. Density structure models beneath the area were constructed by three-dimensional inversion solutions based on the gravity data. As the results, it is inferred that the gravity anomaly and density structures were generally concordant with the distribution of the faults.