Full-waveform inversion of short-offset, band-limited seismic data in the Alboran Basin (SE Iberia)

Abstract

Abstract. We present a high-resolution P-wave velocity model of the sedimentary cover and the uppermost basement to ∼3 km depth obtained by full-waveform inversion of multichannel seismic data acquired with a 6 km long streamer in the Alboran Sea (SE Iberia). The inherent non-linearity of the method, especially for short-offset, band-limited seismic data as this one, is circumvented by applying a data processing or modelling sequence consisting of three steps: (1) data re-datuming by back-propagation of the recorded seismograms to the seafloor; (2) joint refraction and reflection travel-time tomography combining the original and the re-datumed shot gathers; and (3) full-waveform inversion of the original shot gathers using the model obtained by travel-time tomography as initial reference. The final velocity model shows a number of geological structures that cannot be identified in the travel-time tomography models or easily interpreted from seismic reflection images alone. A sharp strong velocity contrast accurately defines the geometry of the top of the basement. Several low-velocity zones that may correspond to the abrupt velocity change across steeply dipping normal faults are observed at the flanks of the basin. A 200–300 m thick, high-velocity layer embedded within lower-velocity sediment may correspond to evaporites deposited during the Messinian crisis. The results confirm that the combination of data re-datuming and joint refraction and reflection travel-time inversion provides reference models that are accurate enough to apply full-waveform inversion to relatively short offset streamer data in deep-water settings starting at a field-data standard low-frequency content of 6 Hz.

Graph‐Space Optimal Transport Concept for Time‐Domain Full‐Waveform Inversion of Ocean‐Bottom Seismometer Data: Nankai Trough Velocity Structure Reconstructed From a 1D Model

“…Furthermore, the resolution of the final FAT model is limited to the first Frenel's zone, which does not guarantee that the model accurately predicts the later arrivals. The problem can be partially mitigated through the joint refraction and reflection traveltime tomography (e.g., Gras et al., 2019) or through the simultaneous inversion of first‐arrival traveltimes and their slopes (horizontal derivatives, e.g., Sambolian, Gorszczyk, et al., 2019; Sambolian, Operto, et al., 2019). The latter approach has the potential to better constrain the model structure, although it requires a proper weighting between the update coming from the first‐break traveltimes and from their slopes.…”

spyro: a Firedrake-based wave propagation and full waveform inversion finite element solver

“…The acoustic wave equation has one free parameter c that is the spatially-variable compressional wavespeed otherwise referred to as the P-wavespeed. The acoustic wave equation is frequently used in FWI applications because its numerical solution is computationally inexpensive compared to the solution of the elastic wave equation while still yielding practically useful inversion results in some scenarios (Gras et al, 2019).…”

“…The construction of models consistent with observations of Earth's physical properties can be posed mathematically as solving an inverse problem referred to as full waveform inversion (FWI) (Lines and Newrick, 2004;Virieux and Operto, 2009;Fichtner, 2011;Brittan et al, 2013). FWI is used extensively in geophysical exploration studies in the search for raw materials such as oil and gas (Gras et al, 2019;Fruehn et al, 2019). The attraction of the FWI approach is the promise of deriving higher fidelity models from acquired seismic data as compared to other less complex and less costly methods (e.g., time travel tomography) (Lines and Newrick, 2004).…”

Reflection tomography by depth warping: a case study across the Java trench

“…For cases where the MCS data do not provide sufficient move-out sensitivity to estimate reliable velocities (i.e. deep target depth), several velocity inversion strategies have been established to combine near-vertical reflections, wide-angle (WA) reflections, and refracted events (Gras et al, 2019;Górszczyk et al, 2019;Melendez et al, 2019).…”