京津冀地区地震重新定位及其与活动断裂的关系

Relocated Seismicity and its Relation with Active Faults in Beijing—Tianjin—Hebei Area

地震重新定位为地震活动和活动构造等研究提供了相对精确的地震参数。本文采用双差地震定位法对京津冀及周边地区2007年12月~2016年3月底的地震进行重新定位,并结合区内的活动断裂资料,探讨重定位后地震的空间分布特征、震源深度分布特征及其与已知活动断裂的关系,并根据重定位后地震空间线性条带的走向揭示隐伏断裂。研究结果表明,重定位后,地震主要集中在唐山、邢台、张渤带西段和文安地区,震中在空间上的分布比由常规地震确定的初始震中更为集中,沿断裂走向更加收敛;震源深度分布更加合理,主要集中在1~20km的中上地壳层;定位结果显示唐山断裂、卢龙断裂为北西倾高角断层,新河断裂为北西向低倾角断层,张北震区、延矾盆地和怀涿盆地断裂、黄庄—高丽营断裂、夏垫断裂等地区的地震活动剖面呈近直立分布;另外,根据重定位后地震的线性分布还刻划出唐山断裂北段的南侧、文安北部两条近NNE方向的隐伏断裂。本文的研究结果对京津冀地区的地震活动、断层构造以及地震孕育发生环境具有重要意义。

The relocation provides relatively accurate seismic parameters for the research of the seismicity and active tectonics. We relocated earthquakes occurred in the Beijing- Tianjin-Hebei and surrounding areas from December 2007 to March 2016 by the doubledifference algorithm. Combined with the active faults data, we discussed spatial and focal depth distribution characteristic and its relationship to known active faults after relocation. Furthermore, we revealed the concealed fault according to space linear belts strike of the earthquake after relocation. The results show that relocated seismicity is concentrated in the Tangshan, Xingtai, west section of the zhangjiakou-bohai belt and Wenan region, the epicenters are more concentrated in space and around the fault planes than conventional seismic initial epicenters, and more reasonable in depth distribution with focal depths mainly concentrated in the 1 -20 km upper crust layer. Relocation result shows that the Tangshan fault and Lulong fault are high angle faults dipping north-west, Xinghe fault is low angle fault dipping north-west. Seismic profile of Zhangbei region is nearly vertical distribution. In addition, according to seismic linear belts after relocation, it is revealed that the south of Tangshan fault and north of Wenan have two nearly NNE direction concealed faults.