Abstract: In this paper,the relation of time,space and intensity characteristics,as well as focal mechanisms of earthquakes to fault activity in Beijing area has been analyzed.A tectonic deformation model for the upper crust of this region is developed in this paper in the light of the quantitative analysis of fault activity.The results show that the earthquakes in this region are distributed mainly along the NWW direction,forming a concentration belt of earthquakes.In addition,several earthquakes of above magnitude M_S 4.5 occurred along the NE-or NEE-trending faults.These two sets of fault form a conjugate fault system,on which earthquakes occur alternately in different active periods,and the average release rate of creep energy corresponds to the occurrence of one M_S 4.2 earthquake per year.The crust of Beijing region can be divided in to the Yanshan,North Shanxi,Taihangshan and Central Hebei blocks,which have an irregular boundary along the NWW direction.Under the action of the NEE-directed principal compressive stress,these NWW-arranged blocks were easily activated,resulting in concentration belts of earthquake of a certain scale along block boundaries.Moreover,earthquakes of above magnitude M_S 4.5 occurred along the conjugated NE-or NEE-trending faults.

Key words: seismic activity, focal mechanism, fault activity, Beijing region

摘要： 通过地震学参数研究构造脆性变形的方法,着重分析了首都圈地区地震活动的“时、空、强”及其震源机制分布特征与断裂活动的关系,展示出该地区断裂活动的定量性规律,由此获得了首都圈地区上地壳变形的物理模型。结果表明:首都圈地区地震活动的“时、空、强”及其震源机制分布特征与断裂活动性质吻合较好,NE或NEE向和NWW向2组断裂构成共轭断裂;沿NWW-SEE向的张家口-渤海湾断裂带两侧形成了燕山块体、晋北块体、太行山块体和冀中块体的基本活动体系;在NWW-SEE向串列状的块体边界上形成一定量的NWW向地震活动密集带,而在与其共轭的NE或NEE向断裂交汇点附近具有发生中强震级以上地震的构造条件。

关键词: 地震活动性, 震源机制, 断裂活动, 首都圈地区