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Title:: Stress Distribution Characteristics of Faults Intersection in Anninghe-Zemuhe Fault Zone and Its Adjacent Area

Author(s):: WU Weiwei; (Sichuan Earthquake Agency,Chengdu 610000,Sichuan,China)

Keywords:: Anninghe-Zemuhe fault zone; faults intersection; stress drop; seismic activity

摘要:: 根据构造活动特性对安宁河—则木河断裂带及周边地区进行分段,利用多地震的断层面解和中小地震的震源参数结果分析不同断层交会区的局部应力场和地震活动特征。结果表明:研究区北段的断裂呈“入”字形交会,具备应力高度集中的局部条件,地震活动频度高、震级偏大,震源应力降普遍较高; 中段上,安宁河空区内部的断裂呈“钝角”形交会,地震活动稀疏,震源应力降偏低,而空区东侧的断裂呈“Y”字形交会,中小地震比较活跃,震源应力降值总体居中; 在研究区南段,多条断裂呈“Y”字形交会,可能不具备应力高度集中的构造条件,虽然地震活动频度高、震级偏大,但震源应力降值总体居中。研究区地震活动和应力分布的分段差异,与断裂间的相互作用形式有关,交叉断层间的变形不协调对局部应力场和地震危险性有较大影响。

Abstract:: According to the characteristics of tectonic activity,we divided the Anninghe-Zemuhe fault zone and its adjacent areas into three sections,and analyzed the local stress field and seismicity characteristics in different fault intersection areas by using the fault plane solutions of multi-earthquakes and the focal parameter results of medium and small earthquakes.The results show that the faults in the northern section of the study area intersect show an “λ” shape,with high stress concentration,high frequency of seismicity,large magnitude,and high stress drops.In the middle section,the faults in Anninghe seismic gap show an “obtuse angle” intersection,with low frequency of seismicity and low stress drops.While the faults on the east side of the seismic gap show a “Y” shape intersection,with high frequency of small and medium earthquakes and middle stress drops.In the south section,faults intersect is in a “Y” shape,which do not have the structural conditions of high stress concentration.Although the seismic activity in this intersect area is high and the magnitudes of the earthquakes are large,the stress drops are generally in the middle.We obtained that the segmental difference in seismic activity and stress distribution in the study area is related to the form of interaction between faults,and the deformation inconsistency between cross faults has a great influence on local stress fields and seismic risk.