Accession Number : ADA185230

Title :   An Investigative Study of the Applicability of Generalized Linear Inverse Theory to Cross-Borehole Geotomography.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s) : Fralick, Dion T.

Report Date : NOV 1986

Pagination or Media Count : 88

Abstract : In geophysical exploration, reconstructing an image that maps the sub-surface characteristics of the earth is known as geotomography. This technique maps the region of interest in terms of some physical property such as signal attenuation or propagation velocity. Interpretation of these images or maps characterizes the geologic structures below the surface of the earth. Data for this type of imaging can be generated through the region of interest using either seismic or electromagnetic energy. In seismic geotomography, an accepted and widely used reconstruction technique is the inversion of travel-time residuals. The travel-time residuals (difference between the calculated and observed arrival times of particular signals) are expressed as a linear function and reduced in a least-squares sense using generalized linear inversion (GLI). The resulting solution provides information leading to the location of sub-surface anomalies. This investigation is concerned with mapping an underground region from data obtained by power measurements from boreholes on either side of the region of interest--a technique known as cross-borehole geotomography. The objective is to adapt and apply the reconstruction technique based on GLI used in seismic tomography to cross-borehole scanning data. To evaluate this technique the resulting image reconstructions is compared with those obtained from the algebraic reconstruction technique.

Descriptors :   *COMPUTERIZED TOMOGRAPHY, *GEOPHYSICS, BOREHOLES, INVERSION, ARRIVAL, TRAVEL TIME, RESIDUALS, MAPPING, LINEAR SYSTEMS, MATRICES(MATHEMATICS), COMPUTER PROGRAMS, LEAST SQUARES METHOD, THESES.

Subject Categories : Geology, Geochemistry and Mineralogy
      Numerical Mathematics
      Computer Programming and Software

Distribution Statement : APPROVED FOR PUBLIC RELEASE