Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS27] Fault Rheology and Earthquake Physics

Thu. May 26, 2016 1:45 PM - 3:10 PM Convention Hall A (2F)

Convener:*Takeshi Iinuma(National Research and Development Agency Japan Agency for Marine-Earth Science and Technology), Yuko Kase(Geological Survey of Japan, AIST), Ryosuke Ando(Graduate School of Science, University of Tokyo), Wataru Tanikawa(Japan Agency for Marine-Earth Science and Technology, Kochi Instutute for Core Sample Research), Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University), Chair:Takeshi Iinuma(National Research and Development Agency Japan Agency for Marine-Earth Science and Technology), Takanori Matsuzawa(National Research Institute for Earth Science and Disaster Prevention)

[SSS27-23] Rupture process during the 2015 Illapel Chile earthquake: Zigzag-along-dip rupture episodes

*Ryo Okuwaki1, Yuji Yagi1 (1.Graduate School of Life and Environmental Sciences, University of Tsukuba)

Keywords:complex rupture process during megathrust earthquake, backprojection, kinematic waveform inversion

We constructed a seismic source model for the 2015 Mw 8.3 Illapel, Chile earthquake, which was carried out with the kinematic waveform inversion method adopting a novel inversion formulation that takes into account the uncertainty in Green’s function, together with the hybrid backprojection (HBP) method enabling us to track the spatiotemporal distribution of high-frequency (0.3–2.0 Hz) sources at high resolution by using globally observed teleseismic P-waveforms. A maximum slip amounted to 10.4 m in the shallow part of the seismic source region centered 72 km northwest of the epicenter and generated a following tsunami inundated along the coast. In a gross sense, the rupture front propagated almost unilaterally northward from the hypocenter at less than 2 km/s, however in detail the spatiotemporal slip distribution also showed a complex rupture propagation pattern: two up-dip rupture propagation episodes, and the secondary rupture episode may have been triggered by the strong high-frequency radiation event at the down-dip edge of the seismic source region. High-frequency sources tended to be distributed at deeper parts of the slip area, a pattern also documented in other subduction-zone megathrust earthquakes that may reflect the heterogeneous distribution of fracture energy or stress drop along the fault. The weak excitation of high-frequency radiation at the termination of rupture may represent the gradual deceleration of rupture velocity at the transition zone of frictional property or stress state between the megathrust rupture zone and the swarm area.