Application of waveform tomography to marine seismic reflection data from the Queen Charlotte Basin of western Canada

Abstract

To obtain a higher resolution quantitative P-wave velocity model, 2D waveform tomography was applied to seismic reflection data from the Queen Charlotte sedimentary basin off the west coast of Canada. The forward modeling and inversion were implemented in the frequency domain using the visco-acoustic wave equation. Field data preconditioning consisted of f-k filtering, 2D amplitude scaling, shot-to-shot amplitude balancing, and time windowing. The field data were inverted between 7 and 13.66 Hz, with attenuation introduced for frequencies ≥ 10.5 Hz to improve the final velocity model; two different approaches to sampling the frequencies were evaluated. The limited maximum offset of the marine data (3770 m) and the relatively high starting frequency (7 Hz) were the main challenges encountered during the inversion. An inversion strategy that successively recovered shallow-to-deep structures was designed to mitigate these issues. The inclusion of later arrivals in the waveform tomography resulted in a velocity model that extends to a depth of approximately 1200 m, twice the maximum depth of ray coverage in the ray-based tomography. Overall, there is a good agreement between the velocity model and a sonic log from a well on the seismic line, as well as between modeled shot gathers and field data. Anomalous zones of low velocity in the model correspond to previously identified faults or their upward continuation into the shallow Pliocene section where they are not readily identifiable in the conventional migration.

Toward a robust workflow for deep crustal imaging by FWI of OBS data: The eastern Nankai Trough revisited

“…Therefore, a third data‐driven strategy based on offset continuation can be implemented, such that the number of wavelengths that are propagated during seismic modeling is progressively increased as the accuracy of the subsurface model improves. The offset continuation and the time‐damping relaxation should be judiciously combined in the data space to jointly perform a layer‐stripping approach [e.g., Shipp and Singh , ; Wang and Rao , ; Takougang and Calvert , ] and the scale continuation in the model space. Such an approach implies that data recorded at short offsets and long recording times (i.e., deep near‐offset reflections) preferably should not be inverted before longer‐offset earlier arrivals (i.e., postcritical reflections) since it might violate the scale continuation condition.…”

Waveform tomography in 2.5D: Parameterization for crooked‐line acquisition geometry

“…Active‐source waveform tomography and full‐waveform inversion have become trusted tools in research [ Takougang and Calvert , ; Malinowski and Operto , ; Kamei et al ., ] and are being increasingly used in industry settings as well. A number of research groups and companies have developed practical massively parallel full‐waveform inversion programs that operate in 3D (e.g., Ben‐Hadj‐Ali et al []; Plessix []).…”

Delineating shallow quick-clay structures using acoustic full-waveform inversion—Case study from southwest Sweden

“…Redistribution subject to SEG license or copyright; see Terms of Use at http://library.seg.org/ Figure 4: The comparison of processed field data (a -shot 57 from Line 1, cshot 17 from Line 5) with synthetic data from the resulting FWI models (bshot 57 from Line 1, d -shot 17 from Line 5). Red arrows point to wide-angle reflections Takougang and Calvert, 2011) and (2) progressively opening the aperture by increasing the time damping factor.…”