Tomographic Investigations at Landfill 4, Hill Air Force Base, Layton, Utah.
Abstract
In support of soil classification objectives related to an on going study of non-linear soil response, tomographic techniques were developed and tested using seismic data. The data were collected at three locations at Landfill 4, Hill AFB, Utah. The site is a land-fill waste site which had been isolated from the prevailing ground-water flow by a slurry trench. The objective of this study was to identify the effectiveness of geophysical techniques for seismic velocity measurements and tomographic/imaging analyses. Seismic data were collected between pairs of 50 ft. deep boreholes on either side of the slurry trench. First break picks were analyzed using an iterative back-projection tomographic technique utilizing curved rays. Initial processing revealed that smearing of velocity anomalies between the boreholes occurred because of non-optimum placement of shots and receivers. Adding reasonable constraints to the inversion, however, showed a low-velocity region, terminating between 35 and 40 ft., at the trench location. Diffraction arrivals travelling around the base of the low-velocity region further constrained its depth. Other minor low-velocity zones, possibly indicating layers with increased silt content, were also indicated by the inversion model. This study showed that cross-borehole tomography can be a useful tool in delineating velocity anomalies roughly perpendicular to paths between the boreholes, but that velocity anomalies parallel to the boreholes will be smeared unless additional constraints are imposed. A modification to the data acquisition technique to help overcome this problem would be to use additional high-energy shot-points on the surface between the boreholes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 23, 1987
- Accession Number
- ADA181289
Entities
People
- Glyn M. Jones
- Vincent J. Murphy