Abstract:

Abstract:  We mapped b value and local recurrence time TL along the 700km long, leftlateral strike slip  XianshuiheAnningheZemuhe fault zone using the relocated microseismicity between 1992 and 2002 that projected onto the cross section to identify the possible locations of asperities Strong variations in b value are observed along the strike of the fault zone, which are consistent with the surface faulting segmentation in geometry The anomalously short local recurrence time TL and low b value estimates appear on the LuhuoDaofu segment of the Xianshuihe fault zone,  the ShimianMianning segment of the Anninghe fault zone, and  the XichangPuge segment of the Zemuhe fault zone, suggesting that these segments may be the relatively active parts that produce relatively larger microearthquakes than average during the inter seismic interval time With the hypothesis that b value is inversely proportional to the stress, we interpret these three segments as the possible asperities on the fault zone, where the future mainshock will be initiated as the high stress has been accumulated there The risk from the ShimianMianning segment is especially noticeable, which is a wellknown historic earthquake gap The anomalously high b value and long TL estimates on the southeastern segment of the Xianshuihe fault zone along QianningKangdingShimian suggest that this segment may be creeping under low stress at present, and no near future mainshock is expected, although both the historic earthquakes and microseismicity are active there

Key words:

Key words: asperity; local recurrence time TL; b value; the XianshuiheAnningheZemuhe fault zone; background seismicity