【摘要】 收集了四川数字地震台网记录的57个远震事件,并从宽频带数字化三分量地震记录中计算出了马尔康(MEK)、都江堰(YZP)、GP江(JJS)、江油(ZJG)、广元(YTS)、康定(GDS)、汉源(XJP)、雅安(MDS)、峨眉山(EMS)、沐川(WMP)、仁寿(YGD)、荣县(HMS)等12个台站下方的远震P波径向接收函数.另外,引入地震勘探中的动校正技术,将各台的接收函数校正到67°的参考震中距处,然后对接收函数进行叠加以增强信号,并把叠加接收函数作为台站下方的平均接收函数.最后,利用台站下的平均接收函数反演得到S波速度结构.反演结果表明:以锦屏山—龙门山断裂为界,其西侧地壳厚达70 km,而东侧仅为50 km左右Moho面在断裂下方形成了一个陡坎;川西地区的地壳速度结构与川中地区差异较大,主要表现在川西地区的中地壳存在厚度为8-22 km的低速层.在都江堰、雅安一带,低速层的厚度最大,其厚度在20-22 km之间,其上地壳为一个坚硬固体,在区域构造应力场作用下,形成了孕育大地震的构造环境.更多还原

【Abstract】 In the paper, R-component receiver functions of P-wave under 12 stations in Sichuan (MEK,YZP,JJS,ZJG,YTS,GDS,XJP,MDS,EMS,WMP,YGD,HMS) were calculated from 3- component broad-band digital recording data of 57 distant earthquakes. Additionally, the moveout correction technique in exploration seismology was introduced to correct the receiver functions to the 67° reference epicentral distance. Then the receiver functions were stacked to punctuate signals, and the stacked functions were used as the mean receiver functions under stations. Finally, the mean receiver functions were used to invert for the S-wave velocity structures under stations. Results showed that the depth of Moho in the west of the JinpingshanLongmenshan fault is as thick as 70 km, but only 50 km in the east, indicative of a sharp discontinuity. The crustal velocity structure in the western Sichuan is different from the structure in the middle of Sichuan, in that a low-velocity layer of 8-22 km exists in the middle-crustal beneath the western Sichuan. The thickness of the low-velocity layer is the largest in the region of Dujiangyan and Ya an, between 20 km and 22 km. The upper crustal in this region behaves as a firm solid, forming the seismogenic background under the action of the regional tectonic stress field.更多还原