TAI Ling-Xue,
GAO Yuan,
LIU Geng et al
.2015.Crustal seismic anisotropy in the southeastern margin of Tibetan Plateau by ChinArray data: shear-wave splitting from temporary observations of the first phase.Chinese Journal Of Geophysics,58(11): 4079-4091,doi: 10.6038/cjg20151116
利用中国地震科学台阵研究青藏高原东南缘地壳各向异性:第一期观测资料的剪切波分裂特征
太龄雪, 高原, 刘庚, 肖卓
中国地震局地震预测研究所, 北京 100036
Crustal seismic anisotropy in the southeastern margin of Tibetan Plateau by ChinArray data: shear-wave splitting from temporary observations of the first phase
TAI Ling-Xue, GAO Yuan, LIU Geng, XIAO Zhuo
Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China
Abstract:The southeastern margin of Tibetan Plateau has relatively complex tectonic movement and strong tectonic deformation, which grows deep fracture and shattered crust. In order to investigate the crustal deformation mechanism in this region, the study uses data obtained from temporary stations in the south part of North-South Seismic Belt set up under the project ChinArray Phase I from June 2011 to March 2013, to compute the seismic anisotropy applying Systematic Analysis Method of shear-wave splitting (SAM method).#br#SAM method is a comprehensive analysis technique for crustal shear-wave splitting, and it divides into three principal phases: calculation of cross-correlation function, time delay correction and polarization analysis check. Firstly, intercept two horizontal components of the waves, and rotate them to calculate the correlation function. When the correlation function reaches a maximum value, the corresponding rotation angle and time delay can be treated as the preliminary polarization of fast shear-wave (PAZ) and time delay of slow shear-wave (δt). Then, according to the preliminary result, do the time delay correction and polarization analysis check. When the polarization pattern is close to the linear after the time delay correction, the calculation results are acceptable and will be the final result.#br#We analyzed 826 data recorded from 67 stations of ChinArray. According to the regional distribution of stations, faults and the result of shear-wave splitting, we divided the study zone into 5 sub areas, A, B, C, D and E. Area A locates at northwest of the study region, including 21 stations. PAZ in this area are relatively complicated, which trend NW, NE, and NEE; area B is on the west of the study region, and also includes 21 stations, PAZ in this area strike to nearly N-S or NEE; area C locates at southwest of the study region, and includes 9 stations, PAZ of most stations are in direction of NE; area D is on the northeast of the study region, and contains 5 stations, PAZ in this area strike to NE or NW; area E locates at northeast of the study region, and includes 11 stations, PAZ of most stations are in direction of NNW. The PAZ in area A, B and C which locate at west of study region, are in direction of NNW, nearly N-S and NE from north to south, which show a trend of clockwise rotation. While D and E area at eastern part strike to NEE and NNW respectively, PAZ in area D may be influenced by the NE strike fault in the region, and PAZ in area E are consistent with the tectonic stress field, also may be affected by the mass faults strikes to N-S or NW. PAZ at most stations strike to the direction of NNE and NE, consistent with the direction of tectonic stress field, but at some stations near faults are affected by the strike of the faults. The result shows that PAZ is varied with the different areas.#br#Complex tectonics and crisscrossed distributions of faults results in complex PAZ spatial distribution. PAZ at most stations are consistent with the direction of tectonic compressive stress field, while at other stations, they are consistent with the direction of fault strike. This study finally obtained more regional distribution details than the early results such as Shi et al.(2006; 2012), who used the permanent stations. However, due to the complicated geological features, characteristics of shear-wave splitting in the crust in this region still need more data and studies to sustain and verify.
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