由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性

根据最近28年的区域台网地震资料,利用b值空间分布及断裂带分段的多地震活动参数值的组合方法,结合历史强震背景,分析了沿川北龙门山-岷山断裂带不同断裂段的现今活动习性,并初步判别出了潜在的强震危险段落。研究结果表明:龙门山断裂带中-南段存在6个具有不同现今活动习性的段落,其中,绵竹-茂县段处于相对高应力背景下的频繁中-小震活动状态,被认为是龙门山断裂带上未来最可能发生强震的地段;江油-平武段处于相对高应力背景下的稀疏中-小震活动状态,未来有可能发生中强地震。而岷山断裂带中的岷江断裂段和虎牙断裂段,以及叠溪隐伏逆断层地区均具有相对偏低的应力水平,可能与其不久前分别发生过大地震和强震有关,未来不太长的时期内复发大地震的可能性较小。

Study on Fault Sliding Behaviors and Strong-earthquake Risk of the Longmenshan-Minshan Fault Zones from Current Seismicity Parameters

Based on seismic data of regional network for the last 28 years and activity background of strong historical earthquakes, we have analyzed current fault sliding behaviors for various segments of the Longmenshan-Minshan fault zones, northern Sichuan, and preliminarily identified the risky fault-segments on which potential strong earthquakes would occur, from the method combining b-value spatial distributions and combinations of multiple seismicity-parameter values. The result shows that 6 fault-segments with different sliding behaviors exist currently along the central-southern portion of the Longmenshan fault zone. Of which, the segment of Mianzhu-Maoxian is now characterized by the sliding of seismicity of frequently moderate to small-size earthquakes under relatively high stress and believed to be the most on the longmenshan fault zone for strong earthquakes occurring in the future; And the segment of Jiangyou-Pingwu is characterized by the sliding of low seismicity of moderate to small earthquakes under relatively high stress, on which moderate-strong earthquakes maybe occur in the future. While, our analysis also indicates that two segments the Minjiang and the Huya segments on the Minshan fault zone, as well as the Diexi segment where a blind-thrust fault would exist, are now all under relatively low stress that are possibly related to the relatively short lapsed times from the latest large or strong earthquakes on the three segments, and hence suggest having little chance for strong earthquake recurring in the future.