Modelling Long-offset Seismic Waves For Sub-basalt Imaging Available to Purchase

Long-offset data are now commonly used in an attempt to improve the sub-basalt image. An indirect boundary element method combined with domain decomposition is presented and used to study seismic wave propagation through basalt at long offsets. A model derived from real streamer data and well logs is used as an input to the modelling code. Several models are considered and compared with real shot gathers. High-amplitude sub-basalt events are observed on the synthetic shot gathers, especially at long-offsets. The amplitude of these events decreases at long offsets as the basalt velocity is increased, though the events are still visible. A rough basalt top appears to generate strong diffractions, though sub-basalt reflections are not strongly affected in near or long-offsets. No such sub-basalt reflections are seen on the real data. Further modelling will determine why this is the case.