张家口-蓬莱断裂带渤海段晚第四纪活动特征

Characters of the Zhangjiakou-Penglai Fault Zone Activity in the Bohai Sea Since Late Quaternary

张家口-蓬莱断裂带是华北地区一条显著的地震带。利用最新获得的高分辨率浅层地震资料研究了渤海海域内该断裂带晚第四纪以来的活动特征。研究表明：在渤海，张家口-蓬莱断裂带主要由沙西断裂、埕北断裂、沙南断裂、沙东北断裂、柏各庄断裂、石臼坨3号断裂、渤中2号断裂和BZ29断裂等一系列NW走向断裂组成，走向在290°—310°之间；在浅罢沉积物中各断裂由多条次级小断裂组成；晚第四纪以来主要表现出强烈的垂向运动特征，具有正断性质；海域各断裂的最新活动时代为晚更新世（Q3）末期-全新世（Q4）初期，并具有相同的活动趋势，在20ka B.P.和60ka B.P.左右活动强烈，统计计算显示平均垂向活动速率分别为0.15mm／a和0.1mm／a，近20000a以来的垂向活动速率超过0.06mm／a。

The Zhangjiakou-Penglai Fault Zone is one of the most famous seismic zones in Northern China. Its activity in the Bohai Sea since the Late Quaternary is studied based on shallow penetrated seismic data which are new and have high resolution. The results indicate that in the Bohai Sea the Zhangjiakou-Penglai Fault Zone is mainly composed of a series of NW-trending faults, including Shaxi Fault, Chengbei Fault, Shanan Fault, Shadongbei Fault, Baigezhuang Fault, Shijiutuo Fault 3, Bozhong Fault 2 and BZ29 Fault. These faults have a striking ranging from 290° to 310°and often consist of several small secondary faults in shallow depositional sequences. They show strongly vertical movement and exhibit a normal mechanism since the late Quaternary. The ages of their latest activities were in the end of late Pleiscene （Q3） to the early Holocene （Q4）. Their activities had the same trending and showed intensively at about 20 ka B. P. and 60 ka B. P. , being 0.15 mm/a and 0.1 mm/a in average vertical slip rates respectively. Since 20 ka B. P. , the vertical slip rates of all these faults are larger than 0.06 mm/a.