Abstract: Geo-slicer method,a newly developed technique for detecting active fault,is designed to take a slice of unconsolidated Quaternary strata whose texture and structure are not destroyed. The Sanhe-Pinggu M8 earthquake of 1679 is the biggest one recorded in Beijing area. The macroscopical epicenter is located around Pangezhuang Village,Xiadian Town,Hebei Province. We successfully applied the geo-slicer method to detecting the rupture of this earthquake near its epicenter. Through our test research,we gained the following knowledge: 1)the detailed deposit structure of the unconsolidated strata can be kept in the geo-slicer; 2)the power unit should be selected to fit to different site conditions,and for Beijing area,a power unit with "grab+vibrant hammer" is better than that with "crane+hammer" ; 3)there is some shortening due to the vibration of the power,but the shortening is generally less than 5%. Moreover,synthesizing the information from the geo-slicers and trench,we found two earthquake events. One is the 1679 earthquake and the other is the one before the 1679. The vertical seismic displacements are 1.4m and 1.2m,respectively.

Key words: geo-slicer, Sanhe-Pinggu earthquake, paleoearthquake, vertical seismic displacement

摘要： 大地切片调查法,就是在不搅动的状态下从地下切出未固结的第四纪浅部地层的垂直断片,它是一种较新的活动断层探测技术。发生在1679年9月2日的三河-平谷8级地震(烈度Ⅺ),是北京及附近地区历史上记录到的最大地震。在该地震的宏观震中——潘各庄附近,运用大地切片调查法对该地震破裂带进行了实验性探测,获得了较好的效果。实验研究表明:大地切片保留了完好的沉积细结构特征;大地切片调查实施时,要选择合适的动力源,对于北京平原这种黏土含量较高的沉积层,挖掘机加振动锤的动力组合优于吊车加振动锤的动力组合;大地切片由于振动会造成一定地层厚度的压缩,但黏土含量较高的北京地区,压缩比例基本<5%。另外,结合探槽和大地切片的对比分析,揭示了最近2次古地震事件,分别是1679年事件和该地震之前的一次事件,两次地震的垂直同震位移分别是1.4m和1.2m。

关键词: 大地切片调查法, 三河-平谷8级地震, 古地震, 垂直同震位移