京西北地区地震重定位及构造特征

Relocation and its tectonic features in northwest Beijing

采用双差定位法对京西北地区(39.5°—41.5°N,113°—117°E)2013年1月1日至2017年12月31日6223次有效地震进行精确定位,得到该区震源分布的精细图像和震源深度剖面图.结果显示,重新定位后地震的水平分布更集中,沿断裂带分布特征更加明显,震中在断裂带呈更明显的条带状、簇状分布,地震与线状的深浅断裂构造的关系密切;大部分地震发生在中上地壳,震源分布为典型震源密集区的空间形态,呈纵深约15 km、直径20—40 km的近圆形"厚饼状".

To study the relationship between earthquake and structure in northwest Beijing,the double difference positioning method was used to precisely locate 6223 effective earthquakes in the northwest region of Beijing(39.5°41.5°N,113°117°E)from January 1,2013 to December 30,2017,and obtain fine images of source distribution and source depth profile in this region.It shows that the horizontal distribution of earthquakes is more concentrated and the distribution characteristics along the fault zone are more obvious.The epicentre is more obvious in the strip and cluster distribution in the fault zone,and the earthquake is closely related to the linear deep and shallow fault structure.Most of the earthquakes occur in the upper and middle crust;Spatial morphology of typical focal areas,a nearly circular“thick pie”with a depth of about 15 km and a diameter of 2040 km.