Characterization of geotechnical parameters from measurements of surface waves at the Kharga Oasis, Egypt

Abstract

The thickness of near surface layers at the Kharga Oasis (in the New Valley, Egypt) is variable across the entire area. The peak frequency of the horizontal to vertical Fourier spectral ratios of ambient vibrations is related to layer interfaces of sufficient impedance contrast. For the determination of shear wave velocity and other geotechnical parameters we applied different active and passive source techniques, including the horizontal to vertical spectral ratio and multichannel analysis of excited surface waves.The ellipticity function is derived from the ambient vibration wavefield while the active experiments are used to obtain the dispersion curves of Rayleigh waves. A set of models representing the velocity models of the sites is then obtained by jointly inverting ellipticity functions and dispersion curves. From the retrieved model characteristics, the geotechnical parameters are determined. The variability of derived parameters reflects the complexity of the geology and the variability of layer thicknesses. The obtained results will be used for the development of a seismic hazard model for the Kharga Oasis.