长清M4.1地震前区域小震调制比异常分析

研究山东内陆地区2008年以来1级以上小震的月相调制效应，并结合地震b值变化进行分析。结果表明，2020-02-18长清M4.1地震前该区存在低b值、高调制比异常，计算综合节面解P轴方位偏转发现，其与小震b值的低值变化时段非常一致。研究区6次4 级以上地震前，有4次出现异常，调制比≥0.33；而2011年和2016年2次范县地震前未出现异常，可能与范县小震集中区受采油作用影响有关。

Analysis of Regional Small Earthquake Modulation Ratio Anomalies before Changqing M4.1 Earthquake

We study the moon phase modulation effect of small earthquakes above M1 in Shandong inland area since 2008, combining with the variation of seismic b value in this area. The results show that there are anomalies of low b value and high modulation ratio in the area before the 2020-02-18 Changqing M4.1 earthquake, and we calculate the deflection phenomenon of P-axis of the composite nodal plane solution, which is very consistent with the variation period of low b value of small earthquakes. In addition, before the 6 earthquakes above M4 in this area, the abnormality of modulation ratio ≥0.33 occurs 4 times. In 2011 and 2016, the two Fanxian earthquakes did not show the above changes, which may be related to the activity mechanism of oil recovery in Fanxian small earthquake concentration area.