Numerical experiments on three dimensional seismic tomography using graph theoretical ray tracing

Numerical experiments on 3-D seismic tomography implemented by graph theoretical ray tracing and conjugate gradient (CG) inversion method for the laterally inhomogeneous media is presented with emphasis on the technique of improving the resolution of the reconstructed image. Graph theoretical ray tr...

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Bibliographic Details
Published in:Geosciences journal (Seoul, Korea) Korea), 2000-12, Vol.4 (4), p.263-270
Main Authors: Cho, Hyun-moo, Baag, Chang-Eob, Jo, BongGon
Format: Article
Language:English
Subjects:
Computation
Configurations
Direction
Elongated structure
Graphs
Image reconstruction
Inhomogeneous media
Inversions
Iterative methods
Mathematical models
Methods
Ray paths
Ray tracing
Sedimentary basins
Seismic engineering
Seismic phenomena
Seismic tomography
Stellar seismology
Tomography
Travel time
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Summary:Numerical experiments on 3-D seismic tomography implemented by graph theoretical ray tracing and conjugate gradient (CG) inversion method for the laterally inhomogeneous media is presented with emphasis on the technique of improving the resolution of the reconstructed image. Graph theoretical ray tracing is efficient and useful for calculating the traveltime of the first arrival seismic signal and the corresponding ray path. It can trace accurate and stable ray path and produce corresponding traveltime even in the complicated 3-D medium in which traditional ray tracing methods fails. In this study, two kinds of forward-star set, the spherical and the cubic, for the graph theoretical ray tracing were designed. The features of each forward-star set were examined. In the spherical forward-star, the angle between two adjacent forward-star nodes is constant as is in the cubic forward-star but the number of forward-star node is about two third of that of the cubic when the same forward-star level is selected. Thus the computation time of ray tracing is reduced using the spherical forward-star set. We employ the CG method for inversion, because it is fast and has a good convergence rate compared with other inversion schemes. In the tomographic process with some source-receiver configurations, the reconstructed images are distorted and elongated when only one direction of source-receiver configuration is used. However, more accurate image was obtained with two directions of source-receiver configuration, especially in orthogonal direction. The numerical simulations with iterative operations of ray tracing and CG inversion for structured models of an spheroidal body and an elongated sedimentary basin show that the technique presented in this paper is useful to reconstruct subsurface image of 3-D inhomogeneous media with small number of iteration.
ISSN:1226-4806
1598-7477
DOI:10.1007/BF02914035