【摘要】 2013年4月20日8时2分,四川龙门山断裂带的雅安芦山发生Ms7.0级地震,震中位于芦山县太平镇和双石镇之间,震源深度13～14km,震中最大烈度达IX级。震中区野外调查发现,尽管房屋建筑损坏较严重,但这次地震没有产生明显的地表破裂构造,仅见少量的地裂缝和喷砂冒水现象。高分辨率遥感图像解译、主余震分布、震源机制解等综合分析认为,该地震是龙门山断裂带西南段一次独立的破裂事件,属于逆冲型地震,沿双石-大川断裂中南段发生破裂,主破裂面西倾,倾角33°～43°,推断芦山地震与龙门山构造带底部滑脱带(13～19km)断坡构造活动有关。历史上,沿双石-大川断裂发生至少2次Ms6～6.5级地震,由此认为芦山地震是龙门山断裂带西南段特征型地震,与汶川地震不同。原地地应力测量和监测数据表明这是汶川地震后龙门山断裂带西南段应力释放的结果。更多还原

【Abstract】 On April 20 , 2013 , an earthquake with a magnitude of Ms7.0shocked the region of Lushan County , Ya’an City , west Sichuan.The epicenter is located in the zone between Shuangshi and Taiping Townships , with a focal depth of about 13～14km.The maximum intensity degree attained IX.Although severe destruction of buildings in the shocked area , field investigation did not find obvious co-seismic surface rupture , except a small quantity of grand fissures with sand liquidation.Integrate analysis of high resolution satellite images , main-and-after shock distribution and focal mechanism shows that this earthquake is an independent reverse faulting event possibly rupturing the southern segment of the Shuangshi-Dachuan fault , along the SW segment of the Longmenshan fault zone.We infer that the main shock may have occurred on a west-dipping ramp ( with dipping angle of 33°～43° ) of a sole décollement beneath the SW Longmenshan , a similar seismotectonic setting of the Wenchuan earthquake.Historically , there recorded at least two earthquakes with magnitude of Ms 6～6.5along the Shuangshi-Dachuan fault , together with the Lushan earthquake , they characterize the fault activity behavior of this fault zone.Insitu stress measurement results show that this earthquake resulted from the brutal release of accumulated crustal stress within the SW segment of the Longmenshan fault zone.更多还原