由构造应力场研究汶川地震断层的分段性

采用构造应力场均匀性对断层或板块边界进行分段的方法, 利用ldquo;裁剪-粘贴rdquo;法给出的余震震源机制解资料, 进一步从应力场角度确定汶川地震发震断层南、 北段分界点位置及南、北段震后应力场. 研究结果表明, 发震断层南、北段分界点位于北川附近, 与先前的研究结果较为一致. 南、 北段震后应力场反演结果显示, 南、北段的最大主应力轴方位均呈北东东向, 且近水平. 南、北段应力场反演的平均拟合残差和置信区间均较大, 主要原因可能是因为南、北段内应力场不均匀性造成的. 因为本文仅由大余震给出了震源断层的一级分段, 南、北段内应做进一步的细分. 

Segmentation of the Wenchuan earthquake fault derived from tectonic stress analysis

This study determined the boundary between southern and northern segments of the Wenchuan earthquake fault based on the analysis of stress field after the main shock. The method of dividing fault or plate boundary into sections by means of stress field uniformity analysis is utilized. Aftershock focal mechanisms were obtained by using ldquo;cut and pasterdquo; (CAP) method, and used to infer the stress field. The results show that the boundary between the northern and southern segments of the seismogenic fault is located nearBeichuanCounty, similar to those from previous studies. The inverted aftershock stress results show that the orientation of maximum principal stress axes for both northern and southern segments is ENE-WSW, and nearly horizontal. The average misfit and confidence level range of stress inversion result are relatively large, probably due to the stress heterogeneity in the northern and southern segments. Since this research only gives a gross segmentation of the seismogenic fault based on focal mechanism determination of large aftershocks, a further division of the northern and southern segments should be studied in detail in future.