Comparing Shear-Wave Velocity Profiles From Inversion of Surface-Wave Phase Velocities with Downhole Measurements: Systematic Differences Between the CXW Method and Downhole Measurements at Six USC Strong-Motion Sites

Abstract

INTRODUCTION Shear-wave velocity profiles are used in a variety of engineering and seismological applications, and several methods are available to determine the velocities, including borehole and surface-wave methods (Woods and Stokoe, 1985; Stokoe et al. , 1988; Stokoe etal. , 1994; Poran et al. , 1994; Poran et al. , 1996). Surface-wave methods offer the advantage of being non-invasive and less costly than boreholes, but their reliability needs to be established by comparison with more direct methods. The best way to do this is a “blind” test in which the velocities determined independently from surface-wave and borehole measurements at the same site are compared. By “blind” we mean that the determination of the shear-wave velocity profile by the two methods were done independently of one another. It is surprisingly difficult to find situations in which the velocity determinations are truly independent of one another. We report on one such case in this paper. In...