利用接收函数探讨新疆几次中强地震的地壳孕育深度

The Discussion on Crustal Seismogenic Depth of Several Moderate Earthquakes in Xinjiang,Using the P-wave Receiver Function

摘要:

在分析2009~2012年新疆地区的远震P波接收函数过程中，发现部分台站的接收函数中存在清晰且能量较强的壳内间断面转换波。本文分别利用接收函数中的壳内间断面和莫霍面转换波，联合接收函数H-κ叠加方法和时间窗滑动方法，分析了2009~2012年新疆6次中强地震震中周围的7个地震台站下方的地壳和上地壳（壳内间断面上方地壳）介质泊松比在地震前后随时间的动态变化情况。结果显示：乌苏、于田和独山子3个地震台站的地壳介质泊松比在对应的3次中强地震前后出现了较为明显且持续的下降过程，下降幅度大于均值误差，变化形态特征呈"V"字型（乌苏台呈双"V"字型），地震发生在"V"字形成的尾端，但其上地壳介质泊松比在地震前后没有出现明显低值异常变化；其他4个地震台站下方的地壳和上地壳介质泊松比在地震前后没有观测到明显低值异常。根据观测结果，推测3次中强地震前后地壳介质泊松比出现低值异常主要源于中下地壳，地壳孕育深度位于中下地壳。

Abstract:

In this paper,we applied H-κ stack method of receiver function and time-window sliding method to convert waves of Moho and intra-crustal discontinuity in the teleseismic P wave receiver functions in Xinjiang region during the period 2009~2012. We also analyzed the crustal and upper crustal media Poisson's ratios variations with time before and after the earthquake at the stations near the epicenter of 6 moderate earthquakes in Xinjiang region during the period 2009~2012. The results show that the crustal media Poisson ratio beneath Wusu,Yutian and Dushanzi seismic stations display a relatively obvious and continuous decline process before and after the earthquake,and the decline range is larger than the mean error. In addition,the morphological variation is in "V" type(Wusu station was double "V" type),and the earthquake occurs at the tail of the "V" formation,while the Poisson ratio of upper crustal media does not show a significantly low value anomalies before and after the earthquake. The Poisson ratio of crustal and upper crustal media beneath 4 other seismic stations does not observe significant low-value anomalies before and after the earthquake. Among the 7 stations,no matter whether the Poisson ratio of crustal media before and after the earthquake has observed obvious low value anomalies or not,there are no obvious low value anomalies variations of Poisson's ratio were observed in the upper crustal media. According to the observations in this study,it may indicate that the low value anomalies by the Poisson ratio in the crustal media before and after the three earthquakes may stem from the middle and lower crust,indicating that the crustal seismogenic depths of the 3 moderate earthquakes are located in the middle-lower crust.