Dual threshold search method for asperity boundary determination based on geodetic and seismic catalog data

As an important model for explaining the seismic rupture mode, the asperity model plays an important role in studying the stress accumulation of faults and the location of earthquake initiation. Taking Qilian-Haiyuan fault as an example, this paper combines geodetic method and b-value method to propose a multi-source observation data fusion detection method that accurately determines the asperity boundary named dual threshold search method. The method is based on the criterion that the b-value asperity boundary should be most consistent with the slip deficit rate asperity boundary. Then the optimal threshold combination of slip deficit rate and b-value is obtained through threshold search, which can be used to determine the boundary of the asperity. Based on this method, the study finds that there are four potential asperities on the Qilian-Haiyuan fault: two asperities (A1 and A2) are on the Tuolaishan segment and the other two asperities (B and C) are on Lenglongling segment and Jinqianghe segment, respectively. Among them, the lengths of asperities A1 and A2 on Tuolaishan segment are 17.0 km and 64.8 km, respectively. And the lower boundaries are 5.5 km and 15.5 km, respectively; The length of asperity B on Lenglongling segment is 70.7 km, and the lower boundary is 10.2 km. The length of asperity C on Jinqianghe segment is 42.3 km, and the lower boundary is 8.3 km.