龙门山地震带5.12汶川地震余震空间分布特征

Spatial Distribution Characters of Aftershocks of 5.12 Wenchuan Earthquake in Longmenshan Seismic Belt

2008年5月12日14时28分至10月12日12时，四川省汶川发生Ms8．0级地震后共记录到余震33308次，Ms≥4．0级余震268次。采用GIS技术，对龙门山地震带上汶川、北川、青川3个县从2008年5月12日～10月12日12时发生的156次Ms≥4．0级余震的空间分布进行了研究。结果显示：在汶川、北川、青川3个县境内：①在东西方向上，若干余震点位的连线与纬线平行，Ms≥4．0级余震呈现纬向地带性特征；②Ms≥4．0级余震亦呈现经向地带性特征；③Ms≥4．0级余震，最位在南北方向与东西方向的连线形成了经纬交织的网格，在空间上呈现等间距网络状分布现象；④Ms≥4．0级的156次余震均发生在经纬交织的网络节点处及其附近，在空间上具有原地复发性的特点。研究结果对于该地震带的趋势分析和震，精监视有一定的意义。

The 5.12 Wenchuan Earthquake in Sichuan, rupturing the front of the Longmenshan Fault, has reached a magnitude of Ms 8.0, with its aftershocks of 33 308 recorded from May 12 to October 12 in 2008, and 268 aftershocks reaching the magnitudes, Ms≥4.0. In order to present the spatial distribution characters of its aftershocks in Longmenshan Seismic Belt, this paper, supported by the applications of GIS and statistic data, has analyzed 156 aftershocks（Ms≥4.0） that occurred in Wenchuan, Beichuan, and Qingchuan counties during this period. The results show： in 3 counties, （1） in the east west direction, each line connected with a number of aftershocks is closely parallel to respective latitude line. In brief, the aftershocks had some strip zonal characteristics that are parallel to latitude line. （2） The magnitudes of aftershocks（Ms≥4. 0） also had some strip zonal characteristics that are parallel to longitude line. （3） The lines parallel to latitude direction interlinked with those parallel to longitude direction, so aftershocks in these 3 counties present a spatial character of ＂chess＂ shape. （4） All of the aftershocks occurred in the vicinity of the network nodes. This implies that aftershocks obey a law of repeated occurrence in the original location. These useful research conclusions had some definite instructions for analysing the trend and monitoring the seismic risks of aftershocks in all Longmenshan Seismic Belt.