西宁盆地周围区域中小地震震源机制解的计算及其构造意义  

Analysis the tectonics significances and calculation the focal mechanism solutions of middle-small earthquakes in Xining basin and its adjacent area

作　　者：屠泓为[1] 万秀红[1,2] 赵燕杰[1] 高慧慧[1] 孟凡博[1] 丁宁霞[1] 

机构地区：[1]青海省地震局,西宁810001 [2]兰州地震研究所,兰州73000

出　　处：《地球物理学进展》2014年第1期148-154,共7页Progress in Geophysics

基　　金：中国地震局星火计划(XH12051Y);青海省地震局地震研究基金(2012A);留学基金联合资助

摘　　要：采用震中距范围约200km内的P波初动资料，确定了西宁盆地及邻近区域2008～2011年发生的62个ML2．3～5级的中小地震的震源机制，并统计了与震源机制解对应的主应力轴的方向性等参数．结果显示，地震性质主要显示为逆断层和走滑断层，小震的震源机制解虽然具有一定的随机性．北部区域应力场计算结果表明P轴方位角可确定范围为47°～52°，仰角为4°～5．5°，T轴方位角可确定范围为142°～148°，仰角为43°～45°；南部区域应力场计算结果表明P轴方位角可确定范围为155°～255°，仰角为1°左右，T轴方位角可确定范围为0°，仰角为89°～90°综合数据结果显示，北部区域地震的性质以逆走滑为主，南部区域较为复杂，但显示出地震性质仍以逆断层性质为主．从区域应力场统计特征来看，看似无规律的小震震源机制实质上主要受北东-西南向压缩应力及北西西-东南东方向上的拉张应力所控制．分析表明，在区域应力场的构造背景下，地震（尤其是小地震）的震源机制解可能存在多样性，但大量样本反映的主应力轴仍然与该区域内的构造背景一致．这一现象可为相关工作，如小区域震源机制解和余震震源机制解的统计等方面研究，提供必要的借鉴和参考．Use the initial motion P wave within 200km of the distance from epicenter to station, we calculated 62 focal mechanism solutions of ML 2. 3-5 from 2008 to 2011 in Xining basin and its adjacent area, then summed the main stress parameter according to the focal mechanism. The result shows, the small earthquakes＇ focal mechanism have some random characteristics, The north region appears that the P axis azimuth range is 47°-52°,and its elevation range is 4°-5. 5°; the T axis zimuth range is 142°- 148°, and its elevation range is 43°-45°. The southern part shows that the P axis zimuth range is 155°- 255°, and its elevation range is-1°; the T axis azimuth range is-0°, and its elevation range is 89°-90°. The main characteristic of earhtuqake fault is thrust and strike-slip in north part, and the south part is very complicated, but the main characteristic of earthquake fault is thrust, however, according the characteristic of regional stress field, though it seems irregular in surface, but in fact, it still under the control of NEWS＇ pressure and NWW-ESE＇ s tension stress. The analysis shows, under the regional stress field, earthquake （especially small quakes） may appear diversity, but, if with large samples, the main stress still in according with the background＇ s. This phenomenon can be useful reference in related research, such as, for micro-region stress and aftershock＇s focal mechanism research.

关 键 词：西宁盆地 P波初动 震源机制解 应力场状态 计算和分析 

分 类 号：P315[天文地球—地震学]