Abstract
Abstract Pingwu County, which is located at the northern end of the Longmenshan fault structural belt, has an active regional geological structure. For a long time, the Longmenshan fault tectonic belt has become intensely active with frequent earthquakes. According to the existing geological data, the Pingwu–Qingchuan fault passes through the urban area of Pingwu. However, because of the great changes in the original landform of Pingwu caused by the construction activities in this urban area, a precise judgment of the location of the Pingwu–Qingchuan fault according to the new landform characteristics is difficult. Here, the seismic reflection method, electrical resistivity tomography (ERT), and drilling method were used to determine the accurate location of the buried active faults in Pingwu County. The seismic reflection method and ERT are used to determine the location of faults, the thickness of overlying strata of the fault, and the basic characteristics of faults. The drilling data can be used to divide the bedrock lithology and confirm the geophysical results. The geological model of the faults can be constructed by 3D inversion of ERT, and the structural characteristics of the faults can be viewed intuitively. The results of this study can provide a basis for earthquake prevention and construction work in Pingwu. The finding also shows that seismic reflection method and ERT can effectively explore buried active faults in urban areas, where many sources of interferences may exist.
Highlights
Pingwu County is located at the northern end of the Longmenshan fault structural belt, in which intense regional geological tectonic activity has been reported [1,2,3] (Figure 1a)
According to the geological survey and 1:2,00,000 scale geological map of China, we speculate that the Qingchuan–Pingwu fault passes through the urban area of Pingwu County
Studies are rare regarding the active faults identified in urban areas, which are identified by using geophysical prospecting methods
Summary
Pingwu County is located at the northern end of the Longmenshan fault structural belt, in which intense regional geological tectonic activity has been reported [1,2,3] (Figure 1a). Ngac.cn/), we speculate that the Qingchuan–Pingwu fault passes through the urban area of Pingwu County. The engineering of buildings has greatly changed the original landforms of urban areas, and the traditional geologically based methods of fault identification may be insufficient. The geophysical exploration methods have become an effective solution for the identification of buried active faults in cities [7]. Many sources of interference (electromagnetism and noise) are present in urban areas due to human activities, which implies that some conventional geophysical methods cannot be applied. (1) The sources of interference in urban areas are strong. Urban human activities, such as transportation, construction, machinery operation, and other sources of vibration, are complex and will interfere with seismic exploration methods. Electromagnetic waves, such as from transmission lines and electromechanical equipment, generated by human activities will seriously interfere with the electromagnetic exploration methods (natural-source magnetotellurics, audio-frequency magnetotellurics, and controlled source audio-frequency magnetotellurics). (2) Urban hardened ground will
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