【摘要】 使用双差地震定位法对首都圈地区39°～4 1°N,115°～118°E范围内1980～2 0 0 0年的2 0 98个小震进行了重新定位,定位均方根残差从重新定位前的1.4 s降到0 .32 s。重新定位后,地震活动多集中分布于北东与北西向断裂的交汇处,或密集成北东与北西向线性分布,与已知活动断裂具有密切的关系。在顺义与延怀盆地一带揭示出几条高角度北西向隐伏活动断裂,长度在10～2 0 km间。小震活动显示的构造信息表明,北西向构造是重要的发震构造,在现今构造变形和地震孕育、发生中,与北东向构造起着同样重要的作用。同时,重定位震源深度分布在东西方向上显示出明显的不均匀性,推测是地壳变形和构造活动强弱在横向变化的一种反映。更多还原

【Abstract】 We relocate 2098 small earthquakes that occurred in the Beijing area (39°～41°N,115°～118°E) from 1980 to 2000 using the double-difference (DD) algorithm to improve relative location accuracy. The rms residual decreases to 0.32 s from 1.4 s before relocation. The relocated seismicity mainly clusters around the intersection part of NE and NW-trending faults, or tends to form NE and NW lineage. Several NW-trending blind faults with lengths of 10～20 km and high dip angle are revealed by the lineage of seismicity near Shunyi and in the Yanqing-Huailai basin, which were undiscovered by both routine locations and previous tectonic study. The tectonic feature revealed by the seismicity indicates that the NW-trending faults are also to be the seismogenic structure, which plays the same role in tectonic deformation and producing larger earthquakes as the NE ones. The maximum depth of the relocated hypocenters varies greatly from west to east in study area, that is from 15 km in the Yanqing-Huailai basin in west to 25 km in the middle part around Beijing, suggesting that there exist dramatic lateral variation of crustal deformation and tectonic activity.更多还原