【摘要】 本文讨论了2017年8月8日九寨沟M_S7.0 (MW6.5)地震之后震源区的地震活动性,并针对震后九寨沟地区架设的4个流动地震台站记录到的地震波形数据进行了剪切波分裂参数的计算,分析了震源区地壳应力场的特征性变化。九寨沟M_S7.0地震的地震活动性表现为:8月8日主震后震源区地震活动明显增强,直至8月22日之后才有所下降,余震震级整体也呈降低趋势,震级多集中在M_S2.0以下。震源区4个流动台站的剪切波分裂结果表明:快波偏振方向近似为东西向,揭示了九寨沟地区的区域应力场方向为近似东西向;区域内慢波延迟时间的平均值为5.04 ms/km,慢波延迟时间在九寨沟M_S7.0地震之后降低,反映了随着余震的发生,地壳应力不断调整,应力持续释放,直至8月底地壳应力场逐渐趋于稳定状态。更多还原

【Abstract】 This paper discussed the seismic activity in the focal area after Jiuzhaigou M_S7.0(M_W6.5) earthquake on August 8,2017,and calculated the shear wave splitting parameters by using the seismic waveform data from four temporary seismic stations in Jiuzhaigou area,then analyzed the characteristic change of crustal stress in the focal area. After the M_S7.0 Jiuzhaigou earthquake,the seismic activity was significantly enhanced in the focal area on August 8,2017.Until after 22 August 2017,the seismic activity dropped slightly;correspondingly,the magnitude of the aftershocks also became smaller,concentrating below M_S2.0. The results of the polarization directions of fast shear wave at four seismic stations in the focal area show that the polarization directions are approximately east-west,which reveals the direction of the regional stress field in Jiuzhaigou area is approximately east-west. Meanwhile,the average value of the time delay of slow shear wave in the studied area is 5.04 ms/km,and after Jiuzhaigou earthquake the time delay of slow shear wave decreased,which reflects the release and adjustment of the crustal stress with the aftershocks occurrence. And thus the stress field in the crust tends to be stable at the end of August.更多还原