日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS05] Induced and triggered seismicity: case-studies, monitoring and modeling techniques

2019年5月26日(日) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:Luca Urpi(Swiss Seismological Service - ETH Zurich)、Enescu Bogdan(京都大学 大学院 理学研究科 地球惑星科学専攻 地球物理学教室)、青木 陽介(東京大学地震研究所)、Francesco Grigoli(ETH-Zurich, Swiss Seismological Service)

[SSS05-P03] Megathrust-inducing azimuthal seismic anisotropy in local and regional crusts

*Tae-Kyung Hong1Junhyung Lee1Ilgoo Kim1Seongjun Park1 (1.Department of Earth System Sciences, Yonsei University)

キーワード:megathrust earthquake, crustal deformation, induced seismicity

Megathrust earthquakes produce large coseismic and postseismic lithospheric displacements. The 2011 M9.0 Tohoku-Oki megathrust earthquakes produced large displacements up to regional distances. The lithospheric displacements directing to the epicenter on the convergent plate boundary developed transient uniaxial tension field over the backarc lithospheres. The Vp/Vs changes display characteristic 2 theta azimuthal variations in the upper crust of the Japanese islands, ranging between -0.0458 and 0.0422. Large lateral variations in Vp/Vs changes suggest medium-dependent perturbation. The lower crust of the Korean Peninsula in distances of ~1300 km displayed coseismic velocity changes of 3 % after the megathrust earthquake. The Vp/Vsratios and seismic velocities recovered gradually over time. Peak Vp/Vs and seismic velocity changes were observed along paths subparallel or subperpendicular to the directions toward the megathrust earthquake. The azimuthal seismic anisotropy may have developed from preferential crack orientation and azimuthal lithostatic stress changes. It appears that recovery of the medium properties may take decades. A series of moderate-sized earthquakes occurred as a consequence of medium response to the temporal evolution of stress field in the Korean Peninsula.