中文摘要：

用双差地震定位法对华北地区（111°-120°E，35°～42°N）1993-2004年6771次地震（1．0≤M≤6．6）重新定位。重新定位后的结果显示：地震活动呈北东与北西向线性分布，与活动断裂关系密切；在新河断裂下方，存在两条走向北东、向西南倾斜的、不同深度的地震活动带，浅部的从地表向下延伸约20km，长60km，深部的从25km到34km，长约40km；83％的地震震源深度位于0～15km范围内，比由常规地震定位法给出的华北地区（7—21km）的震源深度要浅得多，说明华北地区的地震基本都集中在中上地壳中；约有92％的地震震源深度位于1～24km，表明24km是华北地震构造区震源深度的下界。

英文摘要：

We relocuted epicenters of totally 6 771 earthquakes which occurred in North China region （35°- 42°N, 111 °- 120°E） from 1993 to 2004. The relocation shows those formerly randomly-distributed earthquakes are clustered and are aligned tending to the North-East and North-West directions. It follows that there is a close relationship between the seismicity and known major active faults. From the cross sectional profile beneath the Xinhe fault, the relocated seismic sources reveal two seismic belts of different depths. One of them is around 60km long and in the direction of north-east, its depth varies from the surface downwards to 20 km underground. The other is about 40 km in length and is from 25kin to 30 km in depth. At the same time, we found that the 83 percent relocated hypoeenters vary from 0 km to 15 km in depth. This is certainly more shallow than that from the previous studies which are based on the roubine earthquake location, whose average focal depth is within a range of 7 -21km. This result indicates that the contemporary seismicity in North China region is mainly concentrated in the upper and middle crusts. Furthermore, about 92 percent focal depth is ranged from 1 km to 24 km, which is in good agreement with the consensus that the lower bound of the focal depth in North China region is 24 km.