Development of Improved Geophysical Imaging Techniques for Environmental Site Characterization.
Abstract
The objective of this research was to develop geophysical techniques for environmental site characterization: (1) a multi-offset ground penetrating radar profiling technique; (2) a nonlinear seismic refraction traveltime tomography; (3) a 3-D d.c. resistivity tomography; and (4) an electroseismic method. The goals of this project were accomplished successfully and a large amount of field data were collected and modeled for characterizing actual environmental sites. Specifically, we demonstrate that performing GPR surveys with multi-offset geometry can improve the signal-to-noise ratio of subsurface radar reflections. We formulate a nonlinear seismic refraction traveltime tomography to precisely delineate bedrock topography that fits not only traveltime data but also the gradients of traveltime curves. A 3-D d.c. resistivity tomography technique is described for characterizing conductivity distribution in the shallow earth that can map surface measurements to the subsurface. Finally, we present theoretical and numerical techniques for modeling electroseismic waves from a poin source by solving coupled equations of seismic wave propagation, fluid flow, electrical streaming current, and the resulting electromagnetic field. The usefulness of these four techniques for characterizing environmental sites is demonstrated by applications to field data from various sites. The new approaches and algorithms introduced for GPR, seismic refraction tomography, and 3-D resistivity inversion have received wide interest from both the scientific and user communities. The electroseismic method is still a new and potentially powerful technique for subsurface characterization. The theoretical modeling that was done is the first of its kind in this field.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1995
- Accession Number
- ADA308603
Entities
People
- Daria L. Kutrubes
- David P. Lesmes
- Jung M. Lee
- Matthijs W. Haartsen
- Robert J. Greaves
Organizations
- Massachusetts Institute of Technology