Abstract:
Geophysical exploration is a crucial technical approach in surface substrate survey, and different geophysical response signatures are usually exhibited in different surface substrate layers. High-density resistivity method, the microtremor survey, the opposing-coils transient electromagnetic method, and ground penetrating radar were conducted in this study to evaluate the performance and applicability of various geophysical techniques in surface substrate investigation. The surface substrate geophysical survey was conducted in Guang'an area of Sichuan Province, and the interpretation results were cross-validated using borehole logging data. The results are as follows. ① The microtremor survey achieved the smallest deviation from borehole records in delineating surface substrate layering. ② The opposing-coils transient electromagnetic method offered convenient field data acquisition and reliable subsurface stratification. But, some detection blind zones existed in the shallow layers. ③ Ground penetrating radar could effectively reflect interface boundaries through clear electromagnetic wave reflection events, providing superior resolution and layering accuracy, but with limited penetration depth. ④ High-density resistivity method provided a relatively large detection depth and clearly revealed variations in the profile's electrical structure. However, the stratigraphic interface boundary delineation accuracy was relatively limited. The findings could provide practical guidance and references for selecting appropriate geophysical exploration methods in future surface substrate surveys.