Multiscale imaging of complex structures from multifold wide-aperture seismic data by frequency-domain full-waveform tomography: application to a thrust belt
Article first published online: 4 NOV 2004
Geophysical Journal International
Volume 159, Issue 3, pages 1032–1056, December 2004
How to Cite
Ravaut, C., Operto, S., Improta, L., Virieux, J., Herrero, A. and Dell'Aversana, P. (2004), Multiscale imaging of complex structures from multifold wide-aperture seismic data by frequency-domain full-waveform tomography: application to a thrust belt. Geophysical Journal International, 159: 1032–1056. doi: 10.1111/j.1365-246X.2004.02442.x
- Issue published online: 4 NOV 2004
- Article first published online: 4 NOV 2004
- Accepted 2004 August 2. Received 2004 May 28; in original form 2003 August 8
- finite-difference methods;
- thrust belt;
- traveltime and full waveform inversions;
- wide-aperture seismic data
An application of full-waveform tomography to dense onshore wide-aperture seismic data recorded in a complex geological setting (thrust belt) is presented.
The waveform modelling and tomography are implemented in the frequency domain. The modelling part is solved with a finite-difference method applied to the visco-acoustic wave equation. The inversion is based on a local gradient method. Only the P-wave velocity is involved in the inversion. The inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies. This defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images. The linearized waveform tomography requires an accurate starting velocity model that has been developed by first-arrival traveltime tomography.
After specific pre-processing of the data, 16 frequency components ranging between 5.4 and 20 Hz were inverted. Ten iterations were computed per frequency component leading to 160 tomographic models. The waveform tomography has successfully imaged southwest-dipping structures previously identified from other geophysical data as being associated with high-resistivity bodies. The relevance of the tomographic images is locally demonstrated by comparison of a velocity–depth function extracted from the waveform tomography models with a coincident vertical seismic profiling (VSP) log available on the profile. Moreover, comparison between observed and synthetic seismograms computed in the (starting) traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide-angle reflections from southwest-dipping geological structures.
This study demonstrates that the combination of first-arrival traveltime and frequency-domain full-waveform tomographies applied to dense wide-aperture seismic data is a promising approach to quantitative imaging of complex geological structures. Indeed, wide-aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography. This is critical, because the building of the macromodel remains an open question when only near-vertical reflection data are considered.