【摘要】 选取了汶川地震主震后的2008年5月12日—2009年8月31日,震级为3.0≤MS≤5.0的余震4 240次.利用波形互相关方法得到其P波到时,用双差定位方法对其进行定位,最终得到了2 441次重新定位的结果.统计定位误差(两倍标准偏差)在E--W方向为0.4 km,N--S方向为0.4 km,垂直方向为0.7 km.定位结果表明,汶川地震的余震深度集中在10—20 km,震中分布与龙门山中央断裂带的走向关系密切.沿龙门山断裂的地震分布具有明显的分段性,西南段呈水平带状分布,东北段接近垂直分布,且在北川附近存在深度突变.这与龙门山断裂的地震在西南段多表现为逆冲,东北段多表现为走滑的现象相吻合.在深度剖面上地震的空间分布存在分立的特征,通过对比前人在此地区浅层的地震剖面资料,发现地震空间分布与已探知的浅部断层有较好的对应关系.更多还原

【Abstract】 We collected seismic records of 4240 3.0≤MS≤5.0 aftershocks of the 2008 Wenchuan earthquake for the period of 12 May 2008 to 31 August 2009.By using waveform cross-correlation and double-difference method,2441 events of them were relocated.The errors are 0.4 km in horizontal and 0.7 km in vertical direction,respectively.It is found that the depth of aftershocks concentrate in 10—20 km range,and the epicenters distribute close to the strike of the central Longmenshan fault.The aftershock epicenters spread in horizontal belt for southwestern section of the aftershock zone,and in vertical belt for northeastern section.The aftershock depth abruptly change from 20 km to 10 km near Beichuan.This implies that the spatial distribution of aftershocks show different characteristics along Longmenshan fault,confirming the previous viewpoint that the fault is thrust in SW,while strike-slip in NE.Comparison of the aftershock relocation result with the existing shallow seismic exploration profiles reveals that the aftershock belts well match the known shallow geological active faults.更多还原