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

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.