首都圈地震活动构造成因的小震精定位分析

应用双差地震定位法对首都圈及其邻区1980～2004年发生的地震进行重新定位，进行首都圈的地震构造成因分析表明：重定位的地震表现为与区域构造更为密切的“井”字形活动分布，地震震源分布证实了人工地震勘探所推断的深大断裂的存在；首都圈地区的地震多发生于地壳的中、上部，可能存在局域构造块体运动变形和深部构造动力作用的二种不同地震构造成因；地震活动图像表明中强震易发生在上下地壳相交的脆－韧性转换带中，并揭示了首都圈地区潜在的地震空区和陡倾角的隐伏断层.

Relocated seismicity in Big Beijing area and its tectonic implication

The earthquakes occurred in the studied area from 1980 to 2004 were relocated by the double-difference location method.The relocated seismicity is clearly associated with regional tectonics,and is also in agreement with the existence of deep faults imaged by wide-angle and deep seismic reflection profiling.The vast majority of the earthquakes are located in the upper and middle crust,which implies the two potential seismotectonic mechanisms with deep dynamics and local tectonic blocks motion and deformation.The moderate and strong earthquakes tend to occur in the brittle upper crust and ductile-brittle transition in the lower crust.The seismic activities also demonstrate the pattern of seismic gaps and some potential traces of the steep-inclined buried faults in the Big Beijing area.