Shear wave splitting across the ailao shan-red river fault zone, SW China

摘要

A broad band seismic array was set up across the Ailao Shan-Red River (ASRR) fault zone, SW China. The shear wave splitting parameters on SKS and SKKS phases are calculated using the method of Silver and Chan ( 1991) and indicate the polarization direction of 105 +/- 6 degrees and the delay time of 1.68 +/- 0.44 s beneath the ASRR fault zone. Combined with previous studies, the average polarization direction is 110 +/- 19 degrees and the delay time is 1.58 +/- 0.44 s to the SW side of the fault, while the values are 83 +/- 30 degrees and 1.29 +/- 0.29 s to the NE side. This result implies that the upper mantle anisotropy to two sides of the ASRR fault zone are different. Compared with the SE polarization direction observed in the P-S phase and the N-to-S surface movement in GPS data, our results suggest decoupling of the crust and upper mantle beneath the study region.