【摘要】 小地震震源机制的计算及其可靠性评估，对基于大量小地震震源机制数据的地震监测与预报的相关研究及实际应用具有重要的意义.当前，计算小地震震源机制解较为可行的方法主要有利用初动、振幅比、或者初动结合振幅比的方法.这些方法各有优缺点，但综合来看，初动结合振幅比联合反演震源机制对解的约束性更为显著.本研究基于初动结合振幅比联合反演震源机制的FOCMEC方法进行震源机制解计算，并依据最小空间旋转角、初动矛盾比、台站布局、以及新增的P波清晰程度分布校验等多项指标，提出震源机制解选解和可靠性评估的新方法FOCMEC＿GUI.通过实际算例测试验证后，将该方法应用在2023年11月4日广东恩平M_L4.9地震序列震源区的震源机制研究工作中，获得了28个可靠的震源机制解.背景地震活动以走滑型和正断型为主，恩平M_L4.9主震则呈现出正走滑型的特征，余震主要为正走滑型、走滑型及正断型.结合相对定位结果，震中分布围空及震源机制在围空边缘的空间分布特征，推测恩平地震序列的发震机制，可能是在水平为主的背景应力场作用下，由NE苍城—恩平—海陵断裂与凹凸体相互作用所引发.这种相互作用导致了局部拉张效应，并伴随着走滑型应力集中的发震应力场.通过测试和应用实例表明：本研究结合传统小地震震源机制选解和评估方案的基础上新引入P波清晰度分布校验形成的综合选解和可靠性评估新方案具有较高的合理性和可靠性.更多还原

【Abstract】 Accurate calculation and reliability assessment of small earthquake focal mechanisms are crucial for earthquake monitoring and forecasting based on the source characteristics of numerous minor events. Currently,common approaches include using P-wave first-motion polarity, amplitude ratios, or a combination of both. Each method has its strengths and limitations, but joint inversion using both first-motion and amplitude ratios generally provides better constraints. This study uses the traditional FOCMEC method for focal mechanism inversion and introduces a new tool, FOCMEC＿GUI, for reliability assessment. This tool evaluates solutions using metrics such as the minimum spatial rotation angle, P-wave first-motion clarity distribution calibration, the contradiction ratio of first motions, and station geometry. We applied the method to the November 4, 2023,Enping M_L??4.9 earthquake sequence in Guangdong. A total of 28 reliable focal mechanism solutions were obtained.The results indicate that the background seismicity is dominated by strike-slip and normal faulting. The M_L??4.9 mainshock was of a normal–strike-slip type, and the aftershocks mainly exhibited normal–strike-slip, strike-slip,and normal fault mechanisms. Based on the spatial distribution of relocated epicenters and focal mechanisms at the edge of the asperity, we infer that the Enping earthquake sequence was driven by the interaction between concave and convex tectonic bodies and the NE-trending Hailing–Enping–Cangcheng Fault, under a predominantly horizontal stress regime. This interaction produced local extensional effects and stress concentration, facilitating fault slip. The proposed comprehensive selection and reliability assessment scheme—enhanced by the P-wave clarity distribution calibration—demonstrates improved robustness and rationality over traditional approaches.更多还原