Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in reve...Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland. Based on teleseismic SKS and SKKS phases recorded in the seismic stations, we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting. We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers. From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs. These splitting parameters re- veal the complexity of the upper mantle anisotropy image. Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland, with an average shear-wave time delay of 0,95 s; the anisotropy in the western region is slightly larger （1.01 s） than in the eastern region （0.92 s）. On a larger scale, the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode, i.e. the crust-lithospheric mantle coherent deformation. In eastern China, the average fast-wave direction is approximately parallel to the direction of the absolute plate motion; thus, the upper mantle anisotropy can be attributed to the asthenospheric flow. The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions, where the anisotropy images are more complicated, exhibiting ＂fossil＂ anisotropy and/or two-layer anis^3trc^py. The c^llisi（3n between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland, while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.展开更多
基金supported by the National Natural Science Foundation of China(Grants Nos.90914005,91014006,41174070)the Basic Pro-ject in the Ministry of Science and Technology(Grants No.2006FY1101100)
文摘Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland. Based on teleseismic SKS and SKKS phases recorded in the seismic stations, we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting. We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers. From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs. These splitting parameters re- veal the complexity of the upper mantle anisotropy image. Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland, with an average shear-wave time delay of 0,95 s; the anisotropy in the western region is slightly larger （1.01 s） than in the eastern region （0.92 s）. On a larger scale, the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode, i.e. the crust-lithospheric mantle coherent deformation. In eastern China, the average fast-wave direction is approximately parallel to the direction of the absolute plate motion; thus, the upper mantle anisotropy can be attributed to the asthenospheric flow. The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions, where the anisotropy images are more complicated, exhibiting ＂fossil＂ anisotropy and/or two-layer anis^3trc^py. The c^llisi（3n between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland, while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.
