Comparison of Shear-Wave Velocity-Depth Profiles from Downhole and Surface Seismic Experiments

Abstract eng:
We conducted shallow seismic survey at 10 strong-motion stations in Turkey and estimated shear-wave velocities down to a depth of 30 m using the method of multichannel analysis of surface waves (MASW). At each station site, we also drilled a borehole with casing down to 30-m depth and determined a downhole shear-wave velocity-depth profile. We then compared the shear-wave velocity-depth profiles estimated by the MASW and determined by the downhole seismic survey. We also had the opportunity to compare both sets of profiles with the estimates from the spectral analysis of surface waves (SASW) previously reported. An integrated data acquisition system that includes an accelerated impact source with a 50-kg weight, a 48-channel receiver cable with 2-m geophone interval and 4.5-Hz vertical geophones, and two 24-channel, 24-bit Geode recording units was used to acquire the shallow seismic data. We acquired two 48-channel seismic records at each of the station sites using the common-spread recording geometry. By applying Rayleigh-wave inversion to the surface waves isolated from the shot records, we estimated an S-wave velocity-depth profile for the site. For the downhole seismic survey, we used a threecomponent 14-Hz borehole geophone and a shear-wave impact source at the surface, and recorded data at

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