【摘要】 本研究采用双差定位法对2013年4月20日发生在龙门山断裂带上的四川芦山7.0级强震及主震后48小时内504次余震序列进行重新定位,最终得到328个精定位地震事件.结果表明,余震在水平方向上主要沿龙门山断裂带的山前断裂西南段的大川—双石断裂发生,扩展模式以西南向为主(约23km)兼有弱东北向(约12km),并非简单的单侧扩展.在深度方向上,余震主要以铲状结构分布在18～22km之间.通过拟合精定位后的小震空间分布特征,显示本次地震断层面倾角在15～25km深度范围内由主震处约44°逐渐向西南向扩展增大至约73°,可能表明断层往西南破裂过程中走滑分量逐渐增强,与2008年汶川地震引起中央断裂倾角由西南向东北变化相类似.更多还原

【Abstract】 Using the double-difference relocation algorithm,we relocated the April 20,2013 Lushan,Sichuan earthquake(MS7.0) and its 504 aftershocks within 48 hours since the mainshock,and finally obtained 328 relocated earthquakes.Our results show that most aftershocks occurred along the Dachuan-Shuangshi fault which situates at the southwestern end of the front range fault in the Longmenshan fault zone,and their extension is predominated by the southwestward movement about 23 km but with the weak northeastward movement around 12 km,which is not a simple single-sided extension.In depth direction,the aftershocks take as a shovel-shaped structure at 18~22 km depth.Fitting the spatial distribution of relocated aftershocks,the results show that the dipping angle of the fault plane gradually increases from 44° around the mainshock at depth of 15~25 km up to 73° when the rupture of the fault extends southwestward,possibly suggesting a gradual increase of striking-slipping component during the southwest rupturing process.This may be similar to that in the central fault caused by the 2008 Wenchuan earthquake.更多还原