Using finite element and Okada models to invert coseismic slip of the 2008 Mw 7.2 Yutian earthquake, China, from InSAR data |
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Authors: | Chisheng Wang Xinjian Shan Changlin Wang Xiaoli Ding Guohong Zhang Timothy Masterlark |
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Affiliation: | 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Dewai Street, Qijiahuozi, Chaoyang District, Beijing, 100029, China 2. Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China 3. Center for Earth Observation and Digital Earth, Chinese Academy of Science, Kedian Tower F14, No. 9 Beiyitiao Road, Zhongguancun, Haidian District, Beijing, 100190, China 4. Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, Rapid City, SD, 57701, USA
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Abstract: | We invert InSAR from ascending and descending passes of ENVISAT/ASAR data to estimate the distribution of coseismic slip for the 2008 Mw 7.2 Yutian earthquake by separately using uniform finite element models (FEMs), non-uniform FEMs, and analytical elastic half-space (Okada) models. We use the Steepest Descent method and Laplacian smoothing to regularize and estimate the slip distribution for each of these different models. Fault surface ruptures interpolated from Quickbird optical images constrain the strike of the fault. The uniform FEM and Okada models assume a fault embedded in a homogeneous and elastic finite domain or half-space, respectively, while the non-uniform FEM describes a domain with spatially variable elastic properties according to the geological structure of Tibet plateau and Tarim. We find that the estimated slip distribution of the non-uniform FEM is similar to that of the uniform FEM but has a slightly larger moment (~2 %). However, more noticeable discrepancies occur between the slip distributions of the uniform FEM and Okada model, where the slip pattern estimated with the FEM looks more scattered and locates at a lower depth. We conclude that, for the case of the Yutian earthquake, the improvement brought by simulating the distribution of geologic material properties is insignificant. This suggests that the uniform geologic structure of Okada models may be sufficient for simulating large intra-continental earthquakes. |
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