Application of surface wave and micro-tremor survey in landslide investigation in the Three Gorges reservoir area

摘要

The surface wave and micro-tremor survey are new methods of the engineering geophysicalinvestigation. They have been widely used in recent years because they are of low cost and easy operation andthey give the dynamic property of the ground,i.e. the shear wave velocity. This paper discusses the applicationof micro-tremor and surface wave in the Qianjiangping and Shuping landslides of the Three Gorges reservoirarea. For surface wave survey,we analyzed the dispersion of the recorded data and then estimated the shear wavevelocity structure by phase velocity inversion. For micro-tremor survey,we observed the ground micro-tremorsignals,and analyzed them by fast Fourier transform method (FFT). The soil response to frequency of groundmicro-tremor is revealed and the function with frequency-dependence and frequency-selection of micro-tremorfor different foundation strata are investigated. The vertical to horizontal spectra ratio (H/V,Nakamura technique)of micro-tremor observed at the surface was used to evaluate the site's predominant period. All of these haveprovided a more dependable basis for the landslide material classification and for analysis of these hazardousphenomena. The experimental foundation and the deduction process of the method were described in detail.Comparison of the geophysical investigation results with the geological data shows their good agreement,thusproving the applicability of the methods in landslide study.