14. Laboratory Measurements of Velocity and Attenuation in Sediments

Abstract

Introduction Seismic velocities and attenuations collected in the field with, for example, reflection, refraction, and crosshole surveys serve as valuable constraints on subsurface lithology, porosity, permeability, and fluid saturation. Until recently, the measurement resolution of seismic velocities in the shallow subsurface had limited the use of the complete power of seismic attribute analysis in shallow soils. Recent advances in field techniques for seismic measurements in shallow soils (e.g., Bachrach et al., 1998; Bachrach and Mukerji, this volume; Baker et al., 1999; Carr et al., 1998; Steeples et al., 1999) as well as the development of seismic cone penetration tests (SCPT) and other improved geotechnical methods (e.g., Crouse et al., 1993; Boulanger et al., 1998) have begun to permit the application of seismic attribute analysis to shallow soils. Unfortunately, the laboratory studies required for establishing relations between the physical properties of the soils and their seismic properties have not been extended to the low pressures analogous to these shallow depths, so the effects of lithology, fluid saturation, and compaction on seismic (P- and S-wave) properties of shallow soils are largely unknown.