Print Email Facebook Twitter Higher-order source-wavefield reconstruction for reverse time migration from stored values in a boundary strip just one point wide Title Higher-order source-wavefield reconstruction for reverse time migration from stored values in a boundary strip just one point wide Author Mulder, W.A. (TU Delft Applied Geophysics and Petrophysics; Shell Global Solutions International B.V.) Date 2018-01-01 Abstract One way to deal with the storage problem for the forward source wavefield in reverse time migration and full-waveform inversion is the reconstruction of that wavefield during reverse time stepping along with the receiver wavefield. Apart from the final states of the source wavefield, this requires a strip of boundary values for the whole time range in the presence of absorbing boundaries. The width of the stored boundary strip, positioned in between the interior domain of interest and the absorbing boundary region, usually equals about half that of the finite-difference stencil. The required storage in 3D with high frequencies can still lead to a decrease in computational efficiency, despite the substantial reduction in data volume compared with storing the source wavefields at all or at appropriately subsampled time steps. We have developed a method that requires a boundary strip with a width of just one point and has a negligible loss of accuracy. Stored boundary values over time enable the computation of the second and higher even spatial derivatives normal to the boundary, which together with extrapolation from the interior provides stability and accuracy. Numerical tests show that the use of only the boundary values provides at most fourth-order accuracy for the reconstruction error in the sourcewavefield. The use of higher even normal derivatives, reconstructed from the stored boundary values, allows for higher orders as numerical examples up to order 26 demonstrate. Subsampling in time is feasible with highorder interpolation and provides even more storage reduction but at a higher computational cost. To reference this document use: http://resolver.tudelft.nl/uuid:5fae23aa-d79a-4863-911d-c296cc0f6baf DOI https://doi.org/10.1190/GEO2017-0182.1 ISSN 0016-8033 Source Geophysics, 83 (1), T31-T38 Part of collection Institutional Repository Document type journal article Rights © 2018 W.A. Mulder Files PDF geo2017_0182.1.pdf 476.31 KB Close viewer /islandora/object/uuid:5fae23aa-d79a-4863-911d-c296cc0f6baf/datastream/OBJ/view