关键词: 汶川8.0级地震, 龙门山断裂, 川西地震台阵, 接收函数, 地壳各向异性

Abstract: From the teleseismic P-waveform data recorded at the dense mega seismic array deployed in the western Sichuan area by the State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,we investigate the crustal anisotropy beneath the stations using waveform correlation method and weighted stacking method. As a preliminary result,we measured the fast polarization azimuth and time delay of the Ps converted wave in the receiver functions at 4 stations on both sides of Longmen Shan Faults. Our results show:1)The waveform correlation method is better than the weighted stacking method and it turns out not only the fast polarization azimuth,but also the time differences between the fast-and slow-wave; The results obtained by using the weighted stacking method are something undetermined due to that the symmetric axis of the crustal anisotropy medium is unclear previously; Application of both methods will be in favor of judging the reliability of the results. 2)The fast polarization azimuths are consistent each other at the stations in Sichuan Basin,suggesting the crust beneath Sichuan Basin has well integrality and a weak lateral deformation. 3)Taking the epicenter of the Wenchuan earthquake as a boundary,the fast polarization azimuth is parallel with the Longmen Shan Faults on the north side of the Sonpan-Ganzi block,and perpendicular to the faults on the south side. This suggests that under the obstruction of the Sichuan Basin,the soft lower crust beneath the north side of the Sonpan-Ganzi block has a NE direction extended deformation along the Longmen Shan Faults,and the crust on its south side is in the status of compressive deformation perpendicular to the faults. Our results can be used for interpreting the single-side rupture of the Wenchuan earthquake and the aftershock evolution.

Key words: M_S 8.0 Wenchuan earthquake, Longmen Shan Faults, Western Sichuan seismic array, receiver function, crustal anisotropy