华北地区中部地震精定位与构造应力场研究

选取华北地区中部2008年1月至2012年12月741次地震事件的波形文件,读取P波初动极性以及P、S波震相到时.利用波形互相关技术,精确计算地震对到时差,结合读取出的震相到时数据,采用双差定位法,对这些地震进行了重新定位,获得了468个地震的精确重定位结果.相比于初始结果,精定位结果在平面分布上更为集中,沿断裂带分布特征更明显;深度也更为合理.在新河断裂附近,存在明显的地震集中条带,整体走向约为北偏东35°,通过剖面分析,发现该断裂倾角很高.依据地震精定位获取P波射线参数,利用P波初动极性,采用改进的格点尝试法,计算了区内单个地震震源机制解及小震综合断层面解,并结合已有的应力数据,综合分析了区内构造应力环境.结果表明,华北地区中部现今构造应力场保持稳定,为最大主应力轴北东东一南西西向,最小主应力轴北北西-南南东向的走滑型应力状态.

Study on Earthquake Relocation and Tectonic Stress Field in Central North China

The initial P-wave polarities, as well as the arrival times of P-wave and S-wave, were picked out from seismic waveform data of 741 earthquakes occurred in Central North China, from January, 2008 to December, 2012. Adopting double-difference location algorithm and waveform correlation rectification technique, these earthquakes were relocated, and 468 relocation results were obtained. Compared with the initial locations, the results of precise relocation are more concentrated around the fault planes, and more reasonable in depth distribution. There is a remarkble earthquake belt with the strike about N35°E along Xinhe fault. Through earthquakes profile projection, it can be inferred that Xinhe fault has a quite high dip angle. According to the precise relocation results, parameters of P wave ray were determined and used to calculate the focal mechanism solutions and fault plane solutions with the improved grid point test method. Combining with the previous stress data in this region, the tectonic stress environment of central North China were analyzed. The result shows that the tectonic stress field in central North China is quite stable, with maximum principle stress in direction of NEE-SWW and minimum principle stress in direction of NNW-SSE.