Abstract:
As one of the important regional faults in northern Ningxia, the Yellow River fault has controlled the formation and evolution of Yinchuan Basin. This fault is one of the inevitable key points for studying the law of seismic activity and geothermal resource enrichment in Yinchuan plain. At present, the study of the Yellow River fault is very insufficient, and the work is mainly concentrated on surface survey with shallow geophysical exploration in some areas. In this paper, the authors used geological outcrop data as clues and, based on regional 1:200000 gravity data, used advanced geophysical data processing techniques such as wavelet demarcation and oblique derivative to clearly depict the phenomenon that the Yellow River fault has obvious characteristics of "flying geese" plane distribution. The fault is divided into four sub-segments: Lingwu section, Linhe section, Yueyahu section and Lihe section. The CSAMT data of Linhe section and Lingwu section reveal that the main fault and its secondary faults of the Yellow River descend gradually from east to west, i.e., "staircase", with obvious "grading" characteristics. The undercut depth of the Yellow River main fault reaches the upper crust, and the combination of the secondary-scale faults on the profile exhibits a typical "broom" shape. The "seat-like" space of "upward steep, moderately gentle, and downward steep" of each fault is obviously present. Compared with the existing research results, it is found that there are three differences between them, i.e., spreading characteristics, spreading position, and spreading relationship.