[S-SS10] 活断層と古地震

[SSS10-P03] Holocene Slip-Rate on the Eastern Margin Fault Zone of the Yokote Basin and the associated tectonic implications

*SHREYA Arora¹、Hisao Kondo¹、Chiharu Nakase²、Takashi Hosoya² (1.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology 、2.Solution Center, Chuo Development Co., Ltd. )

キーワード：1896 Rikuu earthquake (M7.2), Northeast Japan, Seismic and Borehole Survey, Seismic Hazard Assessment

The Ou Backbone Range (OBR) is one of the most seismically active intraplate regions in northeast Japan. It has been the locus of five large magnitude earthquakes over the past 200 years, including the M7.2 1896 Rikuu earthquake which produced coseismic surface deformation along the northern segment of the Eastern Margin Fault Zone of the Yokote Basin (EFZYB), while the southern segment remained unruptured. Despite extensive paleoseismic investigations along the northern ruptured segment, identification of tectonic landforms, slip rate, and recurrence interval remained unresolved along the southern unruptured segment. We report the first estimate of the long-term slip rate, estimates on the recurrence interval, and the probable number of events across the Omoriyama Fault and Kanezawa Fault which are the thrust faults bounding the Mahiru Mountains of the OBR in the south unruptured segment of the EFZYB. Our results are based on the extensive seismic and borehole survey across the fault traces. Here we will present the preliminary results of the work which bears significant importance to the seismic hazard assessment of the central Tohoku region.