S‐wave velocity from ground roll inversion: Source‐receiver tests and statics

Abstract

Estimating a near-surface S-wave velocity (Vs) structure is important in providing a static solution for multicomponent seismic analysis as well as for geotechnical purposes. We use the Multichannel Analysis of Surface Wave (MASW) method to delineate Vs in the near surface (Park et al., 1998; Xia et al., 1999). We applied the MASW method to seismic datasets acquired at the La Marque Geophysical Observatory at the University of Houston Coastal Center, Galveston County, Texas (Figure 1) in March, 2010. There were two major objectives of our study: 1) to test different sources (a 12 lb sledge hammer versus a truck-mounted accelerated weight drop) and various receivers (planted geophones versus a dragged land streamer) and 2) to determine the near-surface S-wave velocity structure in the area. Another goal is also to compare the resolutions of different dispersion curves created by MASW method for different settings and to investigate the consistency of results. The dispersion curves for the seismic lines with planted receivers have lower noise with compare to the land streamer data. Data from lines having planted geophones contain information from greater depth. One of the reasons is the better coupling of planted geophones. Velocity results are consistent though for both types of receivers for the very near surface (7-8m). Analysis shows that the S-wave velocity ranges from 120220m/sec for first 7-8m and increases up to about 500m/sec at a depth of 18-20m.