2012年6月24日宁蒗-盐源MS5.7地震的剪切波分裂探讨

选用2012年6月24日宁蒗-盐源M_S5.7地震震源区的泸沽湖台站2008年9月—2013年9月连续5年的地震数据进行剪切波分裂计算， 从剪切波分裂参数随时间的变化初步获得了宁蒗-盐源地区的区域应力特征， 以及该地震发生前后地壳应力的特征性变化. 泸沽湖台站快波偏振方向结果显示， 该台站具有NE向和SE向两个优势取向， 与研究区域内断裂的走向相同. 该台站的慢波延迟时间表现出明显的变化， 特别是在宁蒗-盐源M_S5.7地震发生前后. 在宁蒗-盐源地震发生前一年， 泸沽湖台站的慢波延迟时间缓慢地增加， 表明该地区地壳应力逐渐积累； 直到该地震发生前一个月， 泸沽湖台站的慢波延迟时间才开始急剧下降， 表明地壳应力随着地震的发生而迅速释放. 

Discussion on shear-wave spIitting of the June 24,2012 NingIang-Yanyuan MS5.7 earthquake

On June 24 2012， an earthquake with M_S5.7 happened in the junction of Ninglang in Yunnan Province and Yanyuan in Sichuan Province. This paper chose the seismic data recorded by the station LGH from September 2008 to September 2013 to analyze shear-wave splitting of the Ninglang-Yanyuan M_S5.7 earthquake. The regional stress characteristics and the stress changes before and after the earthquake are obtained preliminarily from the change of shear-wave splitting parameters with time. The polarization results of fast shear-wave at the station LGH show that there are two polarization directions， i.e.， NE and SE， which are consistent with the strike of the faults in the studied area. There is a visible change in the delay time of slow shear-wave during the observational five years， especially before and after the M_S5.7 earthquake. One year before the earthquake， the delay time of slow wave slowly increased， suggesting the stress accumulation. Till one month before the earthquake， the delay time of slow wave decreases rapidly， indicating the stress in the crust releases rapidly with the earthquake occurrence.