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对2008年汶川地震序列的横波分裂的时空变化现象进行了研究.通过在横波窗内S波质点运动图的分析,从地震余震区附近台站的近场地震记录中提取了S波分裂的快波偏振方向和快慢波之间的时间延迟.龙门山断裂附近7个台站的S波分裂的结果显示了快波偏振方向的空间分布特征,断裂带东南侧(四川盆地一侧)台站的快波偏振方向总体为北东方向,而在断裂西北侧高原内部的PWU(平武台)则为近东西方向.观测到了快慢波之间到时差的趋势性变化,靠近余震带南端的L5501台的到时差在主震后持续减小,北端PWU台的到时差比主震前明显增大.横波分裂现象主要由台站下方岩层中随应力场方向排列的微裂隙控制,结果显示了主震和余震过程中区域应力场的变化,汶川地震余震活动带南部的应力在主震和余震中得到了释放,地壳应力场在余震带北部集中,导致了PWU台在主震后介质各向异性强度的增强.
The temporal and spatial variations of S-wave splitting in the Wenchuan earthquake sequence in 2008 were studied.The S-wave splitting was extracted from the near-field seismograms near stations in the aftershock area by analyzing the S-wave particle motion map in the S wave window The time delay between wave polarization direction and fast and slow wave.The results of S-wave splitting at 7 stations near the Longmenshan fault show the spatial distribution characteristics of fast-wave polarization direction. The stations on the southeast side of the fault zone The Polarization direction of the fast wave is generally in the NE direction, while the PWU (Pingwu station) in the NW plateau is near the east-west direction. The time difference of PWU station at the northern end of the station significantly increased compared with that before the main shock.The shear-wave splitting phenomenon was controlled mainly by the micro-fractures arranged in the direction of the stress field in the rock below the station and the results showed that the main shock And the change of regional stress field during the aftershock. The stress in the southern part of the aftershock zone of Wenchuan earthquake was released in the main shock and aftershocks, and the crustal stress field concentrated in the northern part of the aftershock zone. To enhance the strength of the opposite sex.