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Slip history of the 2016 Mw 7.0 Kumamoto earthquake: intra-plate rupture in complex tectonic environment

Chen Ji, Jinglai Hao, & Zhenxing Yao

Published August 23, 2016, SCEC Contribution #6859, 2016 SCEC Annual Meeting Poster #235

We have selected 14 3-component strong motion observations, combining with waveforms of teleseismic broadband body waves and long period surface waves of the 2016 Kumamoto mainshock to constrain its temporal and spatial distribution of slip. Our preferred model is composed of Hinagu (dipping 73o) and Futagawa (dipping 60o) fault segments. Rupture initiated at JMA hypocenter on the Hinagu segment in dominant right-lateral strike-slip motion. The significant rupture on the Futagawa segment occurred 4-5 s later at a depth about 10 km with pure strike-slip motion but normal fault component increases as the rupture propagates close to the Aso Volcano. The total rupture duration is 15 s. The best double couple solution of the cumulative moment tensor of this rupture has strike, dip, rake angles of 224o, 64o and -152o, respectively, agreeing remarkably with the long period best double couple solutions of USGS W-Phase solution (224o, 66o, -152o) and the GCMT project (222o, 77o, -163o). However, the CLVD component is not significant, consistent with USGS solution. It is noteworthy that unlike Hinagu segment, the focal mechanisms of Mw>5 foreshocks all have sub-vertical nodal planes and slightly dipping to the southeast, suggesting the Hinagu surface trace associate with two fault planes in depth. This scenario is closely analogous with the relation of 1989 Loma Prieta, earthquake and San Andreas fault. The relationships among the slip distribution, thermal structure near Volcano and background tectonic loading will be addressed.

Key Words
multi-segment rupture, thermal structure

Ji, C., Hao, J., & Yao, Z. (2016, 08). Slip history of the 2016 Mw 7.0 Kumamoto earthquake: intra-plate rupture in complex tectonic environment . Poster Presentation at 2016 SCEC Annual Meeting.

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