Abstract: The magnetotelluric method was used to study the active fault in Shenzhen city.Four magnetotelluric profiles with densified sites were laid out across Shenzhen Fault zone.The remote reference technique was used in both data observing and processing to eliminate the electromagnetic noise near the survey sites,and rather smooth apparent resistivity curves were obtained finally.TM mode data and two-dimensional inversion method as NLCG were used to obtain the electrical structures underground.According to the surficial geology survey results on regional strata and distribution of magmatic bodies and faults,the electrical structures of the depth less than 2000m of each profile were interpreted firstly,two regional faults,namely,the Henggang-Luohu Fault and the Liantang Fault,and seven local faults consistent with the electrical boundaries were verified or found.The strata in the survey area were then related with the change of resistivity.The horizontal electrical slices of depths less than 5000m indicate the Henggang-Luohu Fault and the Liantang Fault bifurcate at the shallow part but tend to merge at depths.

Key words: magnetotellurics, two-dimensional inversion, structure, Shenzhen Fault zone

摘要： 大地电磁测深方法应用于深圳城市活断层的探测,针对深圳断裂带进行了4条剖面的密集点距的大地电磁测量。采用远参考道数据观测与处理技术,尽可能地消除测点附近的电磁噪音影响,得到了较为光滑的视电阻率曲线。二维反演利用TM极化模式数据以及非线性共轭梯度法(NL-CG)获得了地下电性结构。结合已有的区域地层、岩体及断裂构造分布等地表地质成果,对2000m以上的电性剖面进行了分析,证实或发现了与电性分界带对应的2处区域性断裂(横岗-罗湖断裂与莲塘断裂)构造及7处局部断裂构造,并将测区分布的地层与电阻率变化相对应。通过5000m以上不同深度的电性水平切片,进一步反映了电性剖面所展示的局部断裂构造其实是测区主干断裂(横岗-罗湖断裂与莲塘断裂)在浅表的分支,它们在深部表现出趋于统一的展布特征。

关键词: 大地电磁测深, 二维反演, 结构特征, 深圳断裂带