[S-CG52] Dynamics in mobile belts

[SCG52-15] Spatial change in differential stress magnitudes around the source fault before the 2016 Central Tottori Prefecture earthquake

*Yoshihisa Iio¹, Satoshi Matsumoto², Joint aftershock observation group of the Central Tottori Prefecture earthquake (1.Disater Prevention Research Institute, Kyoto University, 2.Kyushu Unicersity)

Keywords:earthquake size, fault edge, stress, aftershock, intraplate earthquake

How is the magnitude of earthquakes determined? In order to solve this important problem, we analyzed the data from the dense aftershock observation network installed in the aftershock area of the 2016 Mw6.2 Central Tottori Prefecture Earthquake. Aftershock mechanism Comparing the stress field estimated from about 10,000 aftershock focal mechanisms and the calculated stress field, it was found that the differential stress before the earthquake is very small both at the horizontal edges of the mainshock fault and at the deeper part of the fault. These results are considered to be stable estimates because they do not largely depend on the slip distribution of the earthquake and the difference in the direction of the principal stress. Concerning the properties around horizontal edges of the mainshock fault, similar results were obtained for the 2000 Western Tottori Prefecture earthquake occurring in the San’in seismic Zone. Thus, these results show that the fault size of large intraplate earthquakes can be determined by region of small differential stress surrounding future seismic faults.