利用台站综合节面解研究华北地区应力场的变化  

Recent change of stress field in North China derived from station composite focal mechanisms

作　　者：郑建常[1] 徐长朋[1] 李冬梅[1] 周翠英[1] Zheng Jianchang;Xu Changping;Li Dongmei;Zhou Cuiying(Shandong Earthquake Agency,Ji’nan 250102,China)

机构地区：[1]山东省地震局,济南250102

出　　处：《国际地震动态》2018年第4期48-57,共10页Recent Developments in World Seismology

基　　金：山东省自然科学基金(ZR2012DQ006);山东省科技发展计划项目(2014GSF120007);中国地震局监测预报司年度大形势跟踪工作经费联合资助

摘　　要：华北块体的动力边界连续发生2008年汶川8.0和2011年日本宫城近海9.0地震。我们基于全国编目系统提供的华北地区2008—2014年的地震观测报告,读取小震初动符号,利用台站综合机制解,首先讨论了区域构造应力的作用模式,结果显示与区域地质研究结论有较好的一致性;然后基于台站综合解的矛盾比,分析了日本"3·11"地震对华北区域应力场的影响。结果显示,矛盾符号比的区域差异反映了地震活动的某些特征,差异变化则可能与区域应力背景下不同的构造条件有关。日本地震前后3年的结果对比分析发现,华北中东部应力场2011年后更加集中;郯庐断裂带和燕山地震带明显受到日本地震的影响。最后我们发现,不同地区的台站矛盾比的下降转折与周边中强或者显著地震事件有很好的对应,说明类似变化可能反映了区域中强地震活动的孕育过程。Two great earthquakes occurred on driving-force boundary of North China tectonic block:the 12 May 2008 Wenchuan M8.0 earthquake&the 11 March 2011 Tohoku M9.0 earthquake.Based on the event observatory report from 2008 to 2014 in North China,which are provided by China Earthquake Networks Center,we pick first motion polarities at the station,and calculate composite focal mechanism for it.From these results,we firstly discussed the faulting model of regional tectonic stress in North China,and found that it agrees with conclusions given in geology.Then we defined R to be a weighted summation of inconsistencies between observed and calculated polarities,and found that variations of R value with regions might reflect some characteristics in local seismicity.Taking Tohuku earthquake as a demarcation line,two 3-year periods are separated.Comparing results from the former periods and the latter,we found that stress fields in the middle-east part of North China become more concentrate after 2011,and Tancheng-Lujiang fault zone and Yanshan-Bohai seismic zone are obviously affected by the Tohoku earthquake.We finally found that,the descend of station inconsistencies ratio R is corresponding to regional middle-strong or remarkable event,which implies that these changes might reflect the seismogenic process of strong shocks.

关 键 词：综合节面解 初动符号 矛盾比 应力场 

分 类 号：P315.727[天文地球—地震学]