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采用震中距范围约200 km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M_L2.3~5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卖质上主要受北东—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.
Based on the P wave initial data about 200 km away from the epicentral distance range, the focal mechanisms of 62 M_L2.3 ~ M5 medium and small earthquakes occurred in the Xining basin and its adjacent areas from 2008 to 2011 were determined. The corresponding principal stress axis directivity and other parameters.The results show that the seismic properties are mainly shown as reverse faults and strike-slip faults, although the focal mechanism solutions of small earthquakes have a certain degree of randomness.The calculation results of the stress field in the northern region show that the P-axis azimuth The range of azimuth of T axis can be determined from 142 ° to 148 ° and the elevation angle is from 43 ° to 45 °. The calculation results of the stress field in the southern region show that the P axis azimuth The angle can be determined from 155 ° to 255 ° with an elevation of about 1 ° and the azimuth of T axis can be defined as 0 ° and the elevation angle from 89 ° to 90 °. The comprehensive data show that the properties of the northern region are inverted antiskid , But the southern region is more complex, but it shows that the seismicity is still dominated by the reverse fault.From the statistical characteristics of the regional stress field, it seems that the seismogenic mechanism of seemingly irregular small earthquakes is mainly compressed by the NE-SW Stress and tensile stress in the North-West-East-East direction In the tectonic setting of regional stress field, there may exist diversity of focal mechanism solutions for earthquakes (especially for small earthquakes), but the principal stress axes reflected by a large number of samples are still consistent with the tectonic setting within the region. This phenomenon may be Related work, such as the study of focal mechanism solution of small area and focal mechanism solutions of aftershocks, provide the necessary reference and reference.