由震源机制解推断唐山地震序列发震断层的分段特征  

Seismogenic fault segmentation of Tangshan earthquake sequence derived from focal mechanism solutions

作　　者：杨雅琼[1] 王晓山[1,2] 万永革[3,2] 盛书中[3] 陈婷[1] 

机构地区：[1]河北省地震局,中国石家庄050021 [2]中国地震局地球物理研究所,中国北京100081 [3]防灾科技学院,中国河北三河065201

出　　处：《地震学报》2016年第4期632-643,658,共12页Acta Seismologica Sinica

基　　金：国家自然科学基金(91214201);河北省地震局地震科技星火计划重点项目(DZ20150428102;DZ20140101002)联合资助

摘　　要：使用唐山地区2002年1月—2015年11月M_L≥2.5地震的255个震源机制解,采用构造应力场均匀性的分段方法对唐山地震序列的发震断层进行分段.在已有唐山地区震源机制解分区特征的基础上,给出了5个参考应力张量,并通过差异显著性的z值检验计算将唐山地震序列的发震断层分为宁河、唐山、滦县和卢龙等4个子段,进而分别对4个子段的应力场进行反演.结果显示:4个子段的最大主压应力方向均呈近EW向,且唐山、宁河和卢龙子段的应力场均表现出较大的拉张分量;唐山、宁河子段的最佳应力张量与唐山主震对唐山断裂带两端点所产生的引张应力场的作用方式一致.此外,唐山子段的应力场符合基于接收函数给出的上地幔物质隆升模型,滦县子段走滑型的应力状态反映了该区的共轭构造运动,卢龙子段的最佳应力张量为正断兼右旋走滑.从当前唐山地震序列发震断层分段的应力场特征可以推断,现今唐山地区的地震活动具有继承性,主要受区域构造应力场和该区深、浅共存的断裂构造体系控制.Based on the method of tectonic stress field homogeneity,this paper determined the segmentation of the seismogenic fault of Tangshan earthquake sequence by using the focal mechanisms of earthquake with M_L≥2.5occurred in Tangshan area from January of 2002 to November of 2015.According to the previous subarea results related to focal mechanisms in Tangshan area,this paper obtained five reference stress tensors,and the seismogenic fault of Tangshan earthquake sequence was divided into four segments,i.e.,Ninghe,Tangshan,Luanxian and Lulong,by the significant difference analysis of z-test of cumulative misfit.The inversion for stress fields of the four segments shows the orientation of maximum principal stress axes is nearly in EW,and the stress filed of the Tangshan,Ninghe and Lulong segments showed a greater tensile component.The best stress tensors of Tangshan and Ninghe segments are consistent with the tensile stress field caused by the Tangshan main shock＇s pulling the northeastern and southwestern ends of Tangshan fault zone.The uplift model of upper mantle material derived from receiver function may also conform to the stress field of Tangshan segment.The strike-slip stress field of Luanxian segment is closely related to the conjugated structure in this area.The best stress tensor of Lulong segment is normal fault with right-lateral strikeslip.From the present characteristics of stress field for the seismogenic fault segmentation of Tangshan earthquake sequence,it is concluded that the seismicity in Tangshan area has inherited the development mode of Tangshan earthquake sequence,and mainly can be controlled by the regional tectonic stress field and the coexistence of deep and shallow faults.

关 键 词：唐山地震序列 震源机制解 构造应力场 发震断层分段 

分 类 号：P315.2[天文地球—地震学]