SciTech Connect

Title: Seismic Velocities Contain Information About Depth, Lithology, Fluid Content, and Microstructure

Seismic Velocities Contain Information About Depth, Lithology, Fluid Content, and Microstructure Recent advances in field and laboratory methods for measuring elastic wave velocities provide incentive and opportunity for improving interpretation of geophysical data for engineering and environmental applications. Advancing the state-of-the-art of seismic imaging requires developing petrophysical relationships between measured velocities and the hydrogeology parameters and lithology. Our approach uses laboratory data and rock physics methods. Compressional (Vp) and shear (Vs) wave velocities, Vp/Vs ratios, and relative wave amplitudes show systematic changes related to composition, saturation, applied stress (analogous to depth), and distribution of clay for laboratory ultrasonic measurements on soils. The artificial soils were mixtures of Ottawa sand and a second phase, either Wyoming bentonite or peat moss used to represent clay or organic components found in natural soils. Compressional and shear wave velocities were measured for dry, saturated, and partially-saturated conditions, for applied stresses between about 7 and 100 kPa, representing approximately the top 5 m of the subsurface. Analysis of the results using rock physics methods shows the link between microstructure and wave propagation, and implications for future advances in seismic data interpretation. For example, we found that Vp in dry sand-clay mixtures initially increases as clay cements the sand grains and fills porosity, but then Vp decreases more » when the clay content is high enough that the clay matrix controls the elastic response of the material. Vs decreases monotonically with increasing clay content. This provides a method for using Vp/Vs ratios to estimate clay content in a dry soil. « less
Authors: ;
Publication Date:
OSTI Identifier:15004635
Report Number(s):UCRL-JC-144792
TRN: US200320%%259
DOE Contract Number:W-7405-ENG-48
Resource Type:Conference
Resource Relation:Conference: Symposium on the Application of Geophysics to Engineering and Environmental Problems 2002, Las Vegas, NV (US), 02/10/2002--02/14/2002; Other Information: PDF-FILE: 15 ; SIZE: 0.3 MBYTES; PBD: 3 Jan 2002
Research Org:Lawrence Livermore National Lab., CA (US)
Sponsoring Org:US Department of Energy (US)
Country of Publication:United States
Language:English
Subject: 01 COAL, LIGNITE, AND PEAT; 58 GEOSCIENCES; BENTONITE; CEMENTS; CLAYS; GEOPHYSICS; LITHOLOGY; MICROSTRUCTURE; PEAT; PHYSICS; POROSITY; ULTRASONIC WAVES; WAVE PROPAGATION