[S-SS15] 地震発生の物理・断層のレオロジー

[SSS15-P26] Stress field estimated from microseismicity in the northeastern edge of the Honshu around the junction between the northeastern Japan arc and the Kurile arc

*前田 純伶¹、松澤 暢²、岡田 知己²、吉田 武義²、小菅 正裕³、片尾 浩⁴、大坪 誠¹ (1.産業技術総合研究所 地質調査総合センター 活断層・火山研究部門、2.東北大学大学院 理学研究科 、3.弘前大学大学院 理工学研究科、4.京都大学 防災研究所 地震予知研究センター )

We report the present stress field in the northeastern edge of Honshu, NE Japan. The northeastern edge is located around the junction between the northeastern Japan arc and the Kurile arc, and is influenced by the subduction of the Pacific Plate and the southwestward movement of the Kuril Forearc Sliver. However, the seismicity is extremely low in this region. In this study, we investigated focal mechanism solutions of the microearthquakes in the northeast edge of Honshu. The focal mechanisms determined in this study are mainly E-W compressional reverse-fault type in the land area, while N-S compressional reverse-fault type in the sea area. We applied the stress tensor inversions to the focal mechanisms. The estimated stress field is the reverse-faulting type with the NE-SW trending maximum compressional stress axis. The direction of the compressional axis around the junction is rotating even in the result of Terakawa and Matsuura (2010). These results suggest that the northeastern edge of Honshu is largely influencedby the southwestward movement of the Kuril Forearc Sliver. In this presentation, we discuss on the spatiotemporal variations of the stress field there estimated from current microseismicity and the paleostress fields inferred from geological structures.
This research project has been conducted as the regulatory supporting research funded by the Secretariat of Nuclear Regulation Authority (Secretariat of NRA), Japan.

Reference:
Terakawa T, Matsu’ura M (2010) The 3-D tectonic stress fields in and around Japan inverted from centroid moment tensor data of seismic events. Tectonics 29:TC6008. doi:10.1029/2009TC002626.