A traveltime reciprocity discrepancy in the Podvin & Lecomte time3d finite difference algorithm |
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Authors: | Ari Tryggvason, Bjö rn Bergman |
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Affiliation: | Department of Earth Sciences, Uppsala University, Villavägen 16, SE-75236;Uppsala, Sweden. E-mail: |
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Abstract: | We have found that the extensively used finite difference scheme time3d produces time fields which are 'asymmetric' in the sense that traveltimes computed to the right of the source are faster than traveltimes computed to the left. All finite difference schemes will, as they are approximations to the wave equation, to some extent fail to obey reciprocity perfectly. We show, however, that the errors in time3d may be significant—and unnecessarily large. An asymmetry in the point source initialization has been identified, and after correction time3d produces time fields with an improved reciprocity. |
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Keywords: | finite difference methods numerical techniques ray tracing seismic velocities tomography |
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