A STUDY OF GEOTOMOGRAPHIC TECHNIQUES FOR VELOCITY ESTIMATION USING CROSSHOLE SEISMIC DATA

Abstract

Tomography is a technique of producing an image of any part of a medium by transmitting abeam of X•-rays, seismic waves, electromagnetic waves, etc., through it onto an adjacent series of receivers; the image results from variations in thick-ness, density and elastic wave parameters of the medium. Basically, Tomography is known as Computer Aided Tomography or CAT scan which has been widely used in medicine.Since, this newly developing technique is efficient and powerful in determining the lateral velocity and absorption inhomogeneities, it is receiving increasing attention as a potentially valuable tool in geophysical exploration and seismology. Mathematical foun-dations of the general tomography problem can be divided into two major classes: series expansion methods and transform methods. Most of the work done in this dissertation employ series expansion approach of tomography which is more applica-ble and efficient in solving geophysical problems. The objective of this work is to study Tarious tomogra- phic techniques using synthetic cross hole seismic data. As a first step towards this, a forward problem is formulated which comprises of 2—dimensional ray tracing in a inhomogeneous medium..