用双差定位结果分析华北地区的地震活动

华北地区北部是阴山—燕山隆起区、 华北平原和太行山隆起的交界处, 区域内地震活跃, 北部有张家口—渤海地震活动带(张渤带), 西邻山西地震活动带。 本研究采用双差定位法对华北地区2006—2009年发生的地震进行重新定位, 结果显示, 近年来华北地区的地震主要集中在北部的张渤带上, 总体呈WNW向分布。 震源深度主要集中在0~20 km的中上地壳, 占地震总数的96.3%, 有大约57.5%的地震分布在10 km以上的地壳内。 张渤带东部的唐山地区是该地震带上地震最密集的地区, 地震分布与区域内的断层有密切关系。 华北平原中南部的邢台地区也是地震相对较密集的区域, 定位结果显示, 邢台地区的新河断裂可能深达Moho面, 在该断裂的下方可能存在速度异常体, 把邢台地区西南部的地震活动从空间上隔离成上下两部分。 沿新河断裂的地震分布出现异常, 在深度10 km处, 地震分布由北东向西南逐渐与上部的地震分离, 震源深度逐渐加深, 最深可达30 km左右。

Relocation of Small Earthquakes in North China Using Double Difference Algorithm

North of Huabei region is the junction of three tectonic elements which are Huabei subsidence, Yanshan uplift, and Taihang uplift. This region is strongly active. Zhangjiakou-bohai seismic belt is in the north of this region, and Shanxi seismic belt is in the west. Using double difference algorithm, earthquakes occurred from 2006 to 2009 are relocated. The results of relocation show that many earthquakes distribute in the Zhangjiakou-bohai seismic belt, and the direction is WNW. The depth of the earthquakes distribution is from 0 to 20 km with a proportion of 96.3%. And the depths of 57.5% earthquakes are above 10 km in the upper crust. Thangshan region is active, and the distribution of the earthquakes is closely related to seismic faults. In the middle of Huabei subsidence, Xingtai region is also active. In this region, the depth of Xinhe fault can reach to Moho. There is abnormal velocity region, in which the distribution of earthquakes is separated into two parts. The distribution of earthquakes is tilted from northeast to southwest, and the focal depth becomes deep gradually.