北京平原夏垫断裂沉积旋回研究

Research on Sedimentary Cycles of Xiadian Fault near Beijing

通过对夏垫断裂下降盘(上盘)第四纪堆积物逐层分析和对比,定性的分析出夏垫断裂下降盘(上盘)距地表10 m范围内,各层的沉积环境和相应的沉积韵律特征。研究发现:由探槽所揭露的地层可以分为7个沉积旋回,每个沉积旋回由上部的细粒层和下部的粗粒层组成,粒度上细下粗;细粒层均为含碳粘土和粉砂质粘土,具有湖相沉积的特点,其沉积环境多为还原环境或弱还原环境;粗粒层一般为细砂、粗砂层,具有快速堆积的特点,其沉积环境多为氧化环境或弱氧化环境;分析认为,断塞沉积所显示的韵律性结构是地震周期性活动的结果,这一研究是揭示夏垫断裂的古地震事件,反演古地震活动并预测其未来行为的基础。

By drilling and contrasting the lithology of Xiadian fault,we completed the qualitative analysis of sedimentary environment and the corresponding sedimentary rhythm characteristics within the scope of 10 meters away from the earth's surface in Xiandian fracture. The result shows that the formation revealed by the trench consists of seven sedimentary series,each of which contains upper fine layers and lower coarse layers. The upper fine layers are commonly constituted by carbonaceous clay and silty clay,showing characteristics of lacustrine sedimentation,and representing the reductive environment. The lower coarse layers generally consist of fine sand and coarse sand,which suggests a fast depositing,and representing the oxidizing environment. Observations suggest that the deposition rhythms were the result of the periodic behavior of the earthquake. This study lays foundation for revealing the paleo earthquake,deducing the process of seismic activity and forecasting its upcoming behavior.