北京平原区南苑—通县断裂南西段结构特征和活动性

南苑—通县断裂是北京市平原区重要的隐伏断裂之一，其结构特征及活动性的研究对于优化北京市国土空间格局及城市地质安全具有重要意义。本文采用可控源大地音频电磁测深和高精度重力勘探，结合钻孔地层剖面及地质年代学测定，对南苑—通县断裂的结构特征及活动性进行深入探讨。研究结果显示：南苑—通县断裂在北京市南部地区具有较好的延展性，其断裂行迹在可控源音频大地电磁测深和重力剖面上得到了良好的反映。通过钻孔地层剖面及钻孔年代学格架分析，发现断裂没有错断中更新统以上地层，推测南苑—通县断裂南西段在中更新世以来不活动。此外，钻孔中新近纪玄武岩的出现也证明了断裂带定位的准确性，推断玄武岩岩浆来源于软流圈地幔的上涌和区域内大断裂的伸展活动共同作用结果。本研究填补了南苑—通县断裂南西段活动性研究的空白，为北京市南部地区城市地质安全和国土空间开发提供了重要的科学支持，具有重要的理论和实践意义。

Study on Structural Characteristics and Activity of the South West Section of Nanyuan-Tongxian Fault in Beijing Plain Area

Nanyuan Tongxian fault is one of the most important hidden faults in Beijing plain area. The study of its structural characteristics and activity is an important work to optimize the spatial pattern of Beijing''s territory and urban geological security. In this paper, the structural characteristics and activity of the Nanyuan-Tongxian fault are discussed by means of controlled source geoacoustic sounding and high precision gravity exploration, combined with drilling and stratigraphic profiling and geochronology measurement. The results show that the Nanyuan-Tongxian fault has good ductility in the southern area of Beijing, and the fault trace is well reflected in the controlled source audio magnetotelluric sounding and gravity profile. Based on the analysis of borehole profile and borehole chronology, it is found that the fault has no strata above the Middle Pleistocene. It is considered that the South west section of Nanyuan Tongxian fault has been inactive since the Middle Pleistocene. The occurrence of Neogene magma in the borehole also proves the accuracy of fault zone location, and it is inferred that the basalt magma originates from the upwelling of the asthenosphere mantle and the extensional activities of the major faults in the region. The research findings of this paper not only fill the gap in the study of the activity of the southern section of the Nanyuan-Tongxian fault, but also provide important scientific support for urban geological safety and land development in the southern part of Beijing, which has important theoretical and practical significance.