Geometric Detection of the Concealed Area of Tazang Fracture with Ground Penetrating Radar

Jianjun Li

Abstract


In order to effectively keep important buildings (structures) away from an active fault and to minimize the earthquake disaster, it is critical to identify the spatial location, distribution and shape of the concealed fault. This is also the key to evaluate seismic risk and hazard.

Located in “Maqu seismic gap” in the eastern part of East Kunlun Fault Zone, Tazang fracture is partially concealed underground, forming a section of concealed fault. Therefore, it is necessary to identify the spatial distribution and shape of the concealed fault with geophysical methods, providing the basis for seismic risk assessment.

Considering that Tazang fault is buried shallowly in the concealed area, this paper attempts to use the ground penetrating radar (GPR). Firstly, the author sets up survey lines at a known geological observation point, and determines the horizon corresponding to the geophysical profile, the equivalent seismic wave of the stratum and other GPR parameters in consideration of the geological profile of known observation point. Secondly, in reference to the parameters acquired from the known geophysical profile, the author interprets the geophysical profiles at other locations, ascertaining the basic properties like corresponding stratigraphic position, the spatial location and shape of the fault, and the burial depth of the upper piercing point, and discusses about the possible geometrical structural of the concealed fault through the analysis of three geophysical profiles and in view of the surface traces.

Furthermore, this paper, on the basis of stratigraphic sequence and ages, analyzes the active age and seismic potential of the concealed area of Tazang fracture, providing useful data for seismic risk assessment. The research proves that GPR is a feasible method to detect the geometrical structure of a concealed fault under shallow overlay.


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References


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