由地震活动参数分析郯城—庐江断裂带中南段现今活动习性及强震、中强震危险性

根据近38年的地震资料,利用地震活动参数值组合、b值空间分布、断裂带分段,结合历史地震及构造背景的综合分析方法,分析了郯城—庐江断裂带中南段现今地震活动习性,判别出潜在的强震、中强震危险段落。研究结果表明:郯城—庐江断裂带中南段存在着6个具有不同现今活动习性的分段落,其中,郯城—泗洪段断层面的现今活动习性处于高应力背景下的相对闭锁状态,是未来最有可能发生强震的段落;九江段于2005年发生了5.7级地震,积累多年的能量已经释放,闭锁状态已被打开,现处于震后震源断层面应力调整阶段,出现了低b值、高应力的状态,因此,短期内不可能再复发中强以上地震;潍坊—莒县段、定远段、合肥—庐江段、宿松段的现今活动则处于低应力水平状态,较短时期内复发中强以上地震的可能性较小。

Modern Activity Characteristics of the Middle and Southern Part of the Tancheng-Lujiang Fault and Risk of Strong and Moderate Earthquakes Based on Seismic Activity Parameter Analysis

According to seismic data recorded in the last 38 years and by using combination of seismic activity parameters,b value spatial distribution,fault division combined with historical background and tectonic earthquake analysis method,the modern seismic activity characteristics of the Tancheng-Lujiang fault is analyzed,the sections are determined having the potential of strong and moderate earthquakes. The analysis results show that there are six sections along the middle and southern part of the fault with different modern seismic activity characteristics. At the Tancheng-Sihong section,the fault plane is at relatively locked state with high stress background and thus there is highest risk of strong earthquakes. At the Jiujiang section where a M5.7 earthquake occurred in 2005,the energy accumulated formany years has been released years and the stresses on the fault plane are at the phase of adjustment with low b-values and high stresses since the locked state has been unlocked. Therefore,there exists no possibility of recurrence of moderate to strong earthquakes in near future years at this section. At the Weifang-Juxian,the Dingyuan,the Hefei-Lujiang and the Susong sections,the fault planes are at a relatively low stress level,small earthquakes have occurred frequently or sparsely,and there is a small probability of moderate to strong earthquakes in the not long future.