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A new method to constrain shallow crustal S-wave velocities based on direct P-wave amplitudes in receiver functions and its application in northeastern Tibet |
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| Authors: | Wang Xu Chen Ling Ling Yuan Gao Yifan Zhang Jianyong Yao Huajian |
| Institution: | 1.State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China ;2.CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China ;3.University of Chinese Academy of Sciences, Beijing, 100049, China ;4.Laboratory of Seismology and Physics of Earth’s Interior and School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China ;5.Mengcheng National Geophysical Observatory, University of Science and Technology of China, Mengcheng, Hefei Shi, 233500, China ; |
| Abstract: | A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following two steps:first, the high-frequency approximate amplitude formula of direct P-waves in P-RFs of individual stations is used to fit the observed amplitude distribution against the ray parameters at different frequencies, and second, the S-wave velocity depth profile beneath each station is constrained according to an empirical correlation between frequency and depth. Unlike traditional inversion techniques, the newly developed method is not dependent on initial velocity models, and the lateral and vertical resolutions of the results are controlled by the interstation distance and the data frequency, respectively. The effectiveness of the method is verified by synthetic tests on various models. The method is then applied to teleseismic P-RF data from a NW-SEtrending linear seismic array extending from the northeastern Tibetan Plateau to the central Sichuan Basin to construct an S-wave velocity image of the shallow crust along the array. The imaged velocity structure is further analysed and compared with the regional geology. In particular, the structural differences of sedimentary basins in the cratonic area of the stable Sichuan Basin and tectonically active belts in northeastern Tibet are investigated. By combining our results with previous observations, the relationship between the surficial geology and deep processes in the study region is also discussed. |
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