【摘要】 2013年4月20日的芦山"4·20"M S7.0地震发生在龙门山断裂带西南段,震中地区分布多条NE向断裂,构造较为复杂。这次地震震源机制解显示为逆冲型地震,破裂面为NE走向,与龙门山断裂带的运动性质和走向一致。地表调查只在大川-双石断裂(前山断裂)和新开店断裂(大邑断裂南段)发现局部分布的NE向地表裂缝、沿地表裂缝分布的喷砂冒水和砂土液化,不规则的边坡开裂等地表变形,以及断裂沿线较严重的滑坡崩塌和房屋破坏。野外调查没有发现明显的地震地表破裂。GPS测量结果显示,此次地震的发震断裂位于芦山县城附近或其以东,而芦山西侧的断裂也可能参与了部分活动。根据野外地质调查、GPS观测、震源机制解、震源深度、余震分布等结果综合判定,芦山7.0级地震的主要发震构造是芦山之下、大川-双石断裂和新开店断裂之间的龙门山前缘滑脱带。此滑脱带在该段的运动导致了这次地震的发生,并可能带动了它上面的大川-双石和新开店等断裂的活动。更多还原

【Abstract】 The April 20,2013,MS7.0 Lushan earthquake occurred along the southwestern part of the Longmen Shan Fault zone.Tectonics around the epicenter area is complicated and several NEtrending faults are developed.Focal mechanisms of the main shock and inversions from finite fault model suggest that the earthquake occurred on a northeast-trending,moderately dipping reverse fault,which is consistent with the strike and slip of the Longmen Shan Fault zone.NE-trending ground fissures and soil liquefaction along the fissures,heavy landslides along the Dachuan-Shuangshi and Xinkaidian Faults were observed during the field investigations.No surface ruptures were found in the field work.GPS data indicate that the fault on which this earthquake occurred is a fault east of or near the Lushan county and the earthquake also triggered slip on the fault west of the Lushan county.Field observations,GPS data,focal fault plane,focal depth,and distribution of the aftershocks suggest,that the seismogenic structure associated with the MS7.0 Lushan earthquake is the décollement beneath the folds of the eastern Longmen Shan.Slip along this decollement generated the earthquake,and also triggered the slip along the Dachuan-Shuangshi and Xinkaidian Faults.更多还原