GEODETIC AND TELESEISMIC CONSTRAINTS ON SLIP DISTRIBUTION OF 2015 MW6.4 PISHAN EARTHQUAKE |
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| Authors: | CHEN Yun-guo HE Ping DING Kai-hua LI Shui-ping WANG Qi |
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| Institution: | 1. Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China;
2. Faculty of Information Engineering, China University of Geosciences, Wuhan 430074, China;
3. Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan 430079, China |
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| Abstract: | On July 3rd, 2015, a MW6.4 earthquake occurred on Pishan County, Xinjiang, located in the front of western Kunlun thrust belt, which is the largest earthquake(MW6.0~7.0)in the past 40 years in this region. In this study, we collected both the near-filed geodetic coseismic deformation observations including 4 GPS sites and one high-resolution ALOS-2 InSAR imagery, and far-field teleseismic P waveforms from 25 stations provided by IRIS/USGS, to invert the fault parameters(strike and dip)and coseismic rupture model of 2015 MW6.4 Pishan earthquake. Using the finite fault theory, a non-linear simulated annealing algorithm was employed to resolve our joint inversion problem. The strike (120°~130°) and dip angle(35°~40°)of optimal models are different from that of some previous studies, and the dip change is strongly constrained by combined data than that of strike. In fixing the geometric parameters of optimal fault model, we also considered data weight(5)(geodetic data/teleseismic P waveforms)and constrained weight from moment and smooth factor(2.5). Clearly, our results indicate that the slip distribution mainly concentrates in the depth range from 9 to 16km and a length range of 20km along the strike direction, which is similar to the spatial distribution of the relocated aftershocks. The maximum slip is~95cm. The seismic moment release is 5.45×1018N·m, corresponding to MW6.42. Compared with the single data set, geodetic data or teleseismic waveform, our joint inversion model could simultaneously constrain the seismic moment and slip distribution well, thus avoiding effectively a lower-resolution rupture distribution determined by teleseismic-only inversion and a bias released moment estimated by the geodetic-only inversion. Importantly, we should consider both the near-field geodetic data and far-field teleseismic data in retrieving the rupture model for accurately describing the seismogenic structure of active fault in western Kunlun region. |
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| Keywords: | GPS InSAR teleseismic waveform coseismic rupture inversion |
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