THREE-DIMENSIONAL S-WAVE VELOCITY DISTRIBUTION BASED ON AMBIENT NOISE ANALYSIS IN EASTERN NORTH |
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| Authors: | GONG Meng XU Xi-wei ZHANG Xin-dong OUYANG Long-bin JIANG Guo-yan DONG Bo |
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| Institution: | 1. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;2. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China;3. Handan Seismostation of Earthquake Administration of Hebei Province, Handan 050061, China;4. Earthquake Administration of Guandong Province, Guangzhou 510070, China;5. Hebei GEO University, Shijiazhuang 050021, China |
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| Abstract: | We apply ambient noise tomography to continuous vertical component broadband seismic data between January 1, 2010 and December 31, 2011from the regional networks of 190 stations deployed by China Earthquake Administration in Hebei, Shanxi and Inner Mengolia. Ambient noise cross-correlations were performed to produce the Green's functions of each station-pair. Firstly, we used the multiple-filter analysis method to extract surface wave group and phase velocity dispersion curves from inter-station paths at periods from 7 to 40s. Then the study area was discretized into a 0.2°×0.2° grid to obtain the group and phase velocity distributions using O'ccam inversion method. After that, three dimensional (3-D) S-wave velocity structures from the surface down to 50km are inverted from group and phase velocities dispersion results. the results of S wave velocity distribution maps generally demonstrate good correlations with surface geological and tectonic features, and they also clearly revealed the lateral velocity variation in the crust. In the mid-upper crust, the basins are clearly resolved with low S wave velocity due to its thick sedimentary layer, and the Taihang and Yanshan uplifts show relative higher S wave velocity distribution. With the increase of depth (>30km), the S wave velocity distribution presents a contrary characteristic compared to that of the shallow layer, and the S wave velocity beneath the Taihang and Yanshan uplifts are much lower than basin areas, which is possibly correlated with the thickness of the crust. 3-D S wave velocity shows a low-velocity zone at~10~20km depth observed beneath the Tanshan-Hejian-Xintai-Cixian belt and Bohai Bay. the low-velocity zone at~20~30km depth beneath the Datong area may be associated with the thermal material in the crust-mantle. Our S wave velocity distribution maps clearly show that Taihang Mountains is not only the boundary of topography and tectonic zone, but also the transition zone of high and low S wave velocity. |
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| Keywords: | ambient noise dispersion curve S wave crustal and uppermost mantle structure |
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