关键词: b值空间分布, 凹凸体, 马边地区, 强震危险性

Abstract: Based on seismic data of the regional network of the last 34 years,we have analyzed current faulting behaviors of major fault zones in Mabian area,southern Sichuan,and preliminarily identified the risky fault-segments on which potential strong and large earthquakes may occur in future,with the method combining the spatial distribution of b-values with activity background of historical strong earthquakes and current seismicity.Our results mainly show:(1)The spatial distribution of b values displays significant heterogeneity in the study area,which reflects the spatial difference of cumulative stress level along various fault zones and segments in the area;(2)Three anomalously low b-value areas with different sizes exist on Mabian-Yanjin Fault zone,these anomalies can be identified as asperities under relatively high cumulated stress levels,in which,two asperities,located at north of Mabian county and Lidian town in western Muchuan county,and near Yanjin at the south end of the fault zone,respectively,may be the potential seismogenic sources of large earthquakes in Mabian area in the near future,and the third asperity with a small size located at southern Suijiang may be the potential strong-earthquake source;(3)An asperity at south-western segment of Longquanshan Fault may be the site of potential moderate to strong earthquakes;and(4)the asperity on the segment between Huangmu town in Hanyuan county and Longchi town in Emeishan city on Jinkouhe-Meigu Fault has potential for moderate to strong earthquakes.

Key words: spatial distribution of b values, asperities, Mabian area, strong earthquake risk