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Direct estimation of rupture depths of earthquake faults from coseismic surface deformation |
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| Authors: | Zhen Fu CaiBo Hu HaiMing Zhang HuiHui Xu YongEn Cai |
| Institution: | 1. Chinese Academy of Geological Sciences, Beijing, 100037, China 2. College of Earth Science, University of Chinese Academy of Sciences, Beijing, 100049, China 3. School of Earth and Space Sciences, Peking University, Beijing, 100871, China |
| Abstract: | The rupture dimensions of earthquake faults are important parameters for characterizing earthquake ruptures and ground motions. Two key parameters to be determined are the rupture depth and dip angle of earthquake faults. Dislocation theory in an elastic half space indicates that if a seismic rupture directly runs up to the ground surface, there exist zero points of horizontal strain in the surface deformation, which correspond to the rupture depths, except for pure strike-slip faults. In this study, we use numerical simulations to investigate the possibility of inferring rupture depths from zero-strain points for cases of buried faults and heterogeneous media. The results show that the correspondence of zero-strain points to the rupture depths can be influenced by the heterogeneity of the underground media and the stress field. For buried faults, the correspondence relationship is approximately valid when the fault depth is <1 km. In addition, the range of earthquake fault dip angles can be estimated by horizontal displacements on the ground. We also study how to determine the rupture depths of faults from InSAR data after large earthquakes, and successfully apply the method to the 2008 Wenchuan earthquake. The method proposed here, which determines the parameters of fault geometry according to surface deformation, is simple and easy to perform. With independent of aftershocks, it can provide valuable constraints to kinematic inversions. |
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