2021年四川泸县MS6.0地震震源参数研究

2021年9月16日四川泸县发生了有记载以来震级最大的地震(M_S6.0). 为了认识该地震的发震机理, 我们综合使用近震和远震波形数据精确测定了2021年泸县地震及M_S≥3.0余震的机制解、深度、水平位置、破裂方向等震源参数.震源机制解结果显示这些地震大多是逆冲型, 伴有少量走滑成分, M_S6.0地震质心深度为4 km, 矩震级为M_W5.25, 两个节面的走向角、倾角、滑移角分别为95°/47°/84°和283°/43°/96°; sPL和sP两个震相的波形拟合结果表明其质心深度在5 km左右. 我们还利用InSAR形变资料获取了M_S6.0地震的质心位置, 然后利用面波到时差相对定位方法确定了其他地震的水平位置. 基于经验格林函数法得到M_S6.0地震破裂方向大致为北西西. 2021年泸县M_S≥3.0地震质心深度在3~5 km, 且质心震中位于页岩气开采注水井3 km以内, 具体的发震机理还需要参考工业生产数据, 通过岩石物理实验和地质力学模拟来进一步研究.

Research on the source parameters of the 2021 Luxian MS6.0 earthquake

On September 16, 2021, a MS6.0 earthquake occurred in the Luxian County, Sichuan Province, which is the largest earthquake ever recorded in this area. To understand seismogenic mechanism of this earthquake, we use regional and teleseismic waveform data to precisely obtain the source parameters of the 2021 Luxian earthquake and its MS≥3.0 aftershocks, e.g. focal mechanism, depth, centroid location, and rupture directivity. Focal mechanism solutions show that most of the earthquakes in the study area have thrusting focal mechanisms, accompanied by a small strike-slip component. The centroid depth of the MS6.0 earthquake is 4 km with a moment magnitude (MW) of 5.25. The strike, dip, rake of the two nodal planes are 95°/47°/84° and 283°/43°/96°, respectively. Waveform modeling of the sPL and sP phases suggests a centroid depth of around 5 km. We also use InSAR deformation data to determine the precise centroid of the MS6.0 earthquake, and thereafter use differential travel times of surface waves to relocate the MS≥3.0 aftershocks. Rupture directivity of the MS6.0 earthquake is in the direction of NWW inferred from an empirical Green's function method. The Luxian earthquake and its aftershocks have centroid depths of 3~5 km and are located within 3 km away from fluid injection wells of shale gas production. To understand their specific seismogenic mechanisms, it is also necessary to take industrial production data, petrophysical experiments and geomechanical simulation into consideration.