Crustal-scale Imaging from Ultra-long Offset Node Data by Full Waveform Inversion - How to Do It Right?
A. Gorszczyk, M. Malinowski and S. Operto
Event name: 78th EAGE Conference and Exhibition 2016
Session: Full Waveform Inversion II - Inversion Strategies
Publication date: 31 May 2016
Info: Extended abstract, PDF ( 2.83Mb )
Price: € 20
We present feasibility of applying full-waveform inversion (FWI) to densely sampled node data for better imaging of complex targets being beyond the reach of typical towed-streamer surveys. We attempt to process the SFJ-OBS ultra-long offset data acquired in the Eastern Nankai Trough region by first-arrival traveltime tomography (FATT) and state-of-the-art frequency-domain acoustic FWI in order to obtain high resolution crustal velocity model. Our efforts were focused on mitigating cycle-skipping and developing robust quality control workflow for this extremely challenging dataset. The starting FATT model was built in an iterative mode with first-arrival picks refinement after initial FWI. Subsequently, we develop a hierarchical, multiscale layer-stripping inversion strategy with simultaneous opening of the inverted offset range and relaxation of the damping constants, coupled with tuning of the pre-whitening of the diagonal pseudo-Hessian. As a result, the cycle-skipping is kept under control and the reliability of the final model manifests by a good data fit (quantified by the time shifts between real and synthetic data calculated using Dynamic Image Warping) and very consistent source wavelets. FWI model shows several prominent geological features and ties well with a PSDM image build from towed-streamer data acquired along the same profile.