【摘要】 对2013年4月20日芦山MS7.0地震主震震中周边29个地震台记录到的震后一年多的微、小余震,利用Hypo71绝对定位方法进行定位,获得了约1 960次地震的震源位置.结果显示,芦山地震余震在平面上主要沿双石—大川分支断裂及其周边分布,在垂向上主要集中在大约5—20km深度之间的两条余震交叉带上.其中一条余震带倾向NW,倾角在12km左右深度发生变化,浅部倾角较陡,该余震带延伸至地表与双石—大川分支断裂和新开店断裂之间的推测隐伏断裂位置相重合;另一条余震带倾向SE,其延伸至地表的位置与双石—大川断裂非常接近,但与该断裂倾向相反.主震震源位置与两条余震带相交的位置接近,且芦山地震主震的两个节面产状与这两条余震带的深部几何形态正好对应,表明芦山地震主震可能是两条余震带所对应的两条断裂同时活动的结果.更多还原

【Abstract】 The absolute earthquake location method(Hypo71)was used to locate micro-and small-aftershocks of 2013 MS7.0Lushan earthquake,which were recorded by 29 stations around the mainshock region for more than one year.Finally we got the epicentral location of about 1 960 aftershocks.Results reveal that aftershocks laterally distribute along Shuangshi-Dachuan branch fault and its surrounding area,and vertically concentrate on two intersecting aftershock belts in depth range of~5—20km.One aftershock belt dips towards NW,and its dip angle becomes steeper at depth about 12 km.This belt’s extrapolation coincides with the buried fault between Shuangshi-Dachuan branch fault and Xinkaidian fault at surface.The other aftershock belt dips towards SE.Its extrapolation is close to Shuangshi--Dachuan fault at surface;however,its dipping direction is opposite to that of Shuangshi--Dachuan fault.The hypocenter of the Lushan main shock locates close to intersect of the two aftershock belts.Two nodal planes of focal mechanism of the main shock correspond well to the geometry of the two aftershock belts,respectively.This seismogenic structural feature implies that Lushan earthquake probably is resulted from simultaneous movement of two faults along the two aftershock belts.更多还原