【摘要】 2000年1月15日姚安MS6.5地震后,云南省地震局在余震区布设的流动数字台网接收到了大量余震序列的数字波形,这为研究姚安地震的性质提供了丰富的资料.由于剪切波经过上地壳传播时的分裂现象反映了上地壳介质的各向异性,因此在对余震事件进行精确定位的基础上,文中应用互相关系数法计算了余震序列剪切波的分裂参数,并对不同台站和不同区域得到的结果进行了分析讨论.主要得到以下结论:余震区的平均快波偏振方向受区域应力场控制,与主震最大水平主压应力方向一致;不同台站与不同区域事件的平均快波偏振方向是有差异的,与区域内的构造变化和应力场调整有关;延时大小受多种因素影响,与剪切波传播时经过介质的性质关系密切.更多还原

【Abstract】 After the M_S=6.5 Yao′an earthquake on January 15, 2000, a large amount of aftershock waveforms were recorded by the Near Source Digital Seismic Network (NSSN) installed by Earthquake Administration of Yunnan Province in the aftershock region. It provide profuses data to systematically analyze the features of the Yao′an earthquake. The crustal anisotropy is realized by shear-wave splitting propagating in the upper crust. Based on the accurate aftershock relocations, the shear-wave splitting parameters are determined by the cross-correlation method, and the results of different stations and regions are discussed in this paper. These conclusions are obtained as follow: firstly, the average fast directions of the aftershock region are controlled by the regional stress field and parallel to the maximum horizontal compressive stress direction. Secondly, the average fast directions of disparate stations and regions are different and vary with the structural settings and regional stress fields. Finally, delay time value is affected by all sorts of factors, which is especially affinitive with the shear-wave propagating medium.更多还原