Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573959
Title: Wave equation methods in cross-well seismic imaging
Author: Pratt, Robert Gerhard
ISNI:       0000 0004 2737 2672
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 1990
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Abstract:
The science of reconstructing geological parameters from exploration crosshole seismic data has been largely limited in the past to the analysis and inversion of arrival times (travel time tomography). However, the high frequency approximation used in travel time tomography is inappropriate in the imaging of structure that has dimensions of the order of the seismic wavelength or less. Wave equation methods are required to account for the scattering effects in the data arising from fine structure. This thesis demonstrates that the application of wave theoretical techniques to frequency domain data provides a way of reducing the scale of the problem. In cases in which the geology consists of only weak perturbations to otherwise homogeneous media, first order diffraction tomography can provide accurate and rapid solutions. In the past most studies have applied diffraction tomography to synthetic data. The robustness of diffraction tomography is demonstrated in this thesis by applying it to form images from ultrasonic data generated in a physical scale model. An important result of this thesis is that the limitations of first order diffraction tomography can be overcome by using frequency domain imaging methods that incorporate numerical wave equation solutions. The modelling technique of finite differences is applied directly to the frequency domain wave equations. The use of high speed, high capacity vector computers allow the resultant matrix equations to be factorized. Wave fields can then be computed for additional source positions at minimal extra cost.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.573959  DOI: Not available
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