2020-01-23四川石渠M S4.3地震震源机制及发震构造研究

Research on Focal Mechanism and Seismogenic Structure of2020-01-23 Shiqu M S4.3 Earthquake in Sichuan Province

基于数字地震台网波形数据,采用gCAP反演方法解算四川石渠M S4.3地震的震源机制。结果表明,最佳双力偶解为节面Ⅰ走向134°、倾角82°、滑动角11°,节面Ⅱ走向42°、倾角79°、滑动角171°;最佳质心深度为9 km,矩震级为M W4.53。为测试震源机制解的稳定性和可靠性,从地壳速度结构、定位误差和数据质量影响等方面进行分析,研究结果表明,这些因素对反演结果影响较小。余震序列展布方向为NW向,主要分布在主震偏北东侧附近,发震断层具有向NE倾的趋势。综合震源区地质构造特征、主震震源机制解和余震序列的空间分布特征,初步判断石渠地震的发震断层面为节面Ⅰ,即长沙贡玛断裂,是一次左旋走滑型地震事件。

Using gCAP method based on waveform data of digital seismic network,we study the focal mechanism solution of 2020-01-23 Shiqu M S4.3 earthquake in Sichuan province.The result shows that strike/dip/slip of nodal plane Ⅰ are 134°/82°/11° and those of nodal plane Ⅱ are 42°/79°/171°, the centroid depth is 9 km and the moment magnitude is M W4.53. The crustal velocity structure, positioning error and data quality are analyzed to test the stability and reliability of the focal mechanism solution. The results show that these factors have little influence on the inversion results. The aftershock sequences are extended along a NW direction, located in the northeast area of main shock, dipping to northeast. According to geological structure characteristics of the source region, the focal mechanism solution of main shock and space distribution of aftershock sequences, we conclude that nodal plane Ⅰ is inferred to the fault plane and the seismogenic fault is Changsha-Gongma fault. The Shiqu M S4.3 earthquake is a left-lateral strike-slip earthquake event.