横断层作用下汶川地震与芦山地震发震机制新探

New Viewpoints of the Seismogenic Mechanism of Wenchuan and Lushan Earthquakes Under the Action of Transverse Fault

在分析龙门山断裂带区域构造背景、青藏高原东缘新构造运动特征的基础上,阐述龙门山断裂带的构造格局,并利用横断层对龙门山断裂带进行分段;同时,对汶川地震与芦山地震的发震机制及其相互关系进行探讨,并对未来强震危险区进行预测。结果表明:汶川地震具有深部构造的控震作用,其深部孕震机制十分复杂,而芦山地震没有明显的地表破裂带,为一次盲逆断层型地震;卧龙—怀远一线为地壳物质运动方向和主断裂走滑方向发生反向的转换带,发生在其两侧的地震是各自独立的,即汶川地震与芦山地震相互独立;汶川地震与芦山地震发震时,龙门山断裂带中未活动的区域存在较高的地震危险性,尤其是卧龙—怀远和小金横断层之间的断块为强震危险区,虎牙断裂与主断裂交汇处也是强震较危险区。

Regional tectonic background of Longmenshan fault zone and characteristic of neotectonic movement in the eastern margin of Qinghai-Tibet Plateau were analyzed;the tectonic framework of Longmenshan fault zone was explained,and the transverse fault was used to segment Longmenshan fault zone;meantime,the seismogenic mechanism of Wenchuan and Lushan earthquakes and their relationship were discussed,and the dangerous area with great earthquake in the future was predicted.The results show that Wenchuan earthquake has the earthquake-controlling function of deep tectonic,and the deep seismogenic mechanism is very complex,but there is no obvious surface rupture in Lushan earthquake,which is a blind reserve-fault earthquake;the movement direction of crustal material and the strike-slip direction of main fault are reversed at Wolong-Huaiyuan,and the earthquakes occur on the sides of Wolong-Huaiyuan are independent,so that Wenchuan and Lushan earthquakes are independent of each other;the inactive area in Longmenshan fault zone during the occurrences of Wenchuan and Lushan earthquakes may have a high seismic risk,especially the fault blocks between Wolong-Huaiyuan and Xiaojin transverse faults are dangerous with great earthquakes,and the intersections of Huya fault and Longmenshan main faults are also dangerouswith great earthquakes.