A hybrid approach to compute seismic travel times in three‐dimensional tetrahedral meshes

ABSTRACT We propose an optimized method to compute travel times for seismic inversion problems. It is a hybrid method combining several approaches to deal with travel time computation accuracy in unstructured meshes based on tetrahedral elementary cells. As in the linear travel time interpolation me...

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Bibliographic Details
Published in:Geophysical Prospecting 2020-05, Vol.68 (4), p.1291-1313
Main Authors: Nasr, Maher, Giroux, Bernard, Dupuis, J. Christian
Format: Article
Language:English
Subjects:
Accuracy
Cells
Computation
Computational efficiency
Computing aspects
Computing costs
Finite element method
Interpolation
Inversion
Nodes
Ray paths
Ray tracing
Seismic modelling
Seismic surveys
Seismics
Shortest-path problems
Tertiary
Topology
Travel time
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Summary:ABSTRACT We propose an optimized method to compute travel times for seismic inversion problems. It is a hybrid method combining several approaches to deal with travel time computation accuracy in unstructured meshes based on tetrahedral elementary cells. As in the linear travel time interpolation method, the proposed approach computes travel times using seismic ray paths. The method operates in two sequential steps: At a first stage, travel times are computed for all nodes of the mesh using a modified version of the shortest path method. The difference with the standard version is that additional secondary nodes (called tertiary nodes) are added temporarily around seismic sources in order to improve accuracy with a reasonable increase in computational cost. During the second step, the steepest travel time gradient method is used to trace back ray paths for each source–receiver pair. Travel times at each receiver are then recomputed using slowness values at the intersection points between the ray path and the traversed cells. A number of numerical tests with an array of different velocity models, mesh resolutions and mesh topologies have been carried out. These tests showed that an average relative error in the order of 0.1% can be achieved at a computational cost that is suitable for travel time inversion.
ISSN:0016-8025
1365-2478
DOI:10.1111/1365-2478.12930