四川紫坪铺水库库区地震剪切波分裂研究

本研究利用四川紫坪铺水库数字地震台网2004年8月17日~2008年5月11日的地震观测波形资料,使用剪切波分裂SAM系统分析方法,获得了四川紫坪铺水库库区8个数字地震台站的快剪切波偏振结果.结果表明,紫坪铺库区台站的快剪切波偏振优势方向主要为NE或NW方向;台站的快剪切波偏振优势方向与区域主压应力方向或活动断裂走向一致;快剪切波偏振方向变化可能与汶川大地震前区域应力场的增加和龙门山断裂带微破裂增加有关,慢剪切波时间延迟的变化与四川紫坪铺水库水位升降变化相关.

The shear-wave splitting study of Sichuan Zipingpu reservoir region

Using seismic data recorded by Zipingpu reservoir Digital Seismic Network from Aug.17, 2004 to May 11, 2008, the dominant polarization directions of fast shear-waves are obtained at 8 digital seismic stations in this region by SAM technique.The results show that dominant directions of polarizations of fast shear-waves are mainly in nearly NE or NW direction in Zipingpu reservoir region. The dominant polarization directions of fast shear-waves are consistent with the strikes of active faults, or regional principal compressive stress.The direction variety of polarization of fast shear-wave are related with the enhancement of regional stress and micro-cracking of Longmenshan fault before Wenchuan earthquake, and there are correlation between delay time of slow shear-wave and water level of Zipingpu reservoir.