Full-waveform inversion strategies using common-receiver gathers for ocean-bottom cable data. Issue 1 (2nd January 2022) - Hwang, Jongha
Abstract : Full-waveform inversion (FWI), which is among the most powerful seismic data processing techniques for imaging subsurface geological structures, has a huge computational cost in proportion to the number of sources. To increase the speed of FWI, we explored the use of common-receiver gathers (CRGs) as an alternative to common-shot gathers (CSGs) as observed data. This approach has the potential to reduce the computational cost of FWI significantly, particularly for ocean-bottom cable (OBC) acquisition. As we match modelled and observed CSGs in CSG-based FWI, we match observed CRGs with modelled CSGs of switched source–receiver geometry in CRG-based FWI. According to the reciprocity principle, CRG FWI based on the steepest descent or Gauss–Newton method yields the same inverted velocity models as CSG FWI for an identical and known source signature applied over whole source positions. However, when the source wavelet is unknown, and changes from one source position to another, each trace of a CRG contains a different source signature, making it difficult to apply conventional source estimation or source-independent methods to CRG FWI. Therefore, in this study, we proposed inversion strategies for CRG FWI in both the time and frequency domains to deal with errors arising from different source wavelets between CRG traces. Then, we used a synthetic example for the Marmousi-II model and a real data example from the North Sea to demonstrate that our strategies for CRG FWI provide very similar inverted velocity models to those obtained from CSG FWI, at a lower computational cost.