Anisotropic traveltime tomography for depth consistent imaging of PP and PS data

Broto, Karine; Ehinger, Andreas; Kommedal, Jan H.; Folstad, P.G.

doi:10.1190/1.1559037

Cited by 21 publications

(15 citation statements)

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“…The choice of the parameter σ is a difficult task. In practice, we use the L ‐curve method (see Hansen 1992), also called the continuation method (Bube & Langan 1994): starting from a large regularization weight, we decrease it regularly to retrieve more and more varying models until the data are fitted with the expected accuracy. The solution model is thus the smoothest model that fits the data up to a certain precision.…”

Section: The Seismic Reflection Tomography Problemmentioning

confidence: 99%

“…In this section, we present an application of constrained reflection tomography to one 2-D line of a 3-D 4C OBC (Ocean Bottom Cable) survey with PP and PS data from bp. 1 Broto et al (2003) have already interpreted and studied this data set using an unconstrained inversion method. The velocity model is described by four velocity layers and five interfaces (cf Fig.…”

Section: -D Pp/ps Data Setmentioning

confidence: 99%

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Constrained optimization in seismic reflection tomography: a Gauss-Newton augmented Lagrangian approach

Delbos¹,

Gilbert

Glowinski

et al. 2006

Geophysical Journal International

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S U M M A R YSeismic reflection tomography is a method for determining a subsurface velocity model from the traveltimes of seismic waves reflecting on geological interfaces. From an optimization viewpoint, the problem consists in minimizing a non-linear least-squares function measuring the mismatch between observed traveltimes and those calculated by ray tracing in this model. The introduction of a priori information on the model is crucial to reduce the under-determination. The contribution of this paper is to introduce a technique able to take into account geological a priori information in the reflection tomography problem expressed as inequality constraints in the optimization problem. This technique is based on a Gauss-Newton (GN) sequential quadratic programming approach. At each GN step, a solution to a convex quadratic optimization problem subject to linear constraints is computed thanks to an augmented Lagrangian algorithm. Our choice for this optimization method is motivated and its original aspects are described. First applications on real data sets are presented to illustrate the potential of the approach in practical use of reflection tomography.

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Section: The Seismic Reflection Tomography Problemmentioning

confidence: 99%

Section: -D Pp/ps Data Setmentioning

confidence: 99%

Constrained optimization in seismic reflection tomography: a Gauss-Newton augmented Lagrangian approach

Delbos¹,

Gilbert

Glowinski

et al. 2006

Geophysical Journal International

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show abstract

“…Considering the poor conditioning of the estimation of the reference velocity models, the matching of PP‐ and PS‐images is generally insured by pairing a priori PP‐ and PS‐reflected events. In standard traveltime tomography, this seriously complicates the picking step (Gerea, Nicoletis and Rakotoarisoa 2001; Stopin 2001; Broto et al 2003), even if some practical solution can be found (Foss, Ursin and de Hoop 2005).…”

Section: Introductionmentioning

confidence: 99%

2D PP/PS‐stereotomography: Application to a real 2D‐OBC dataset

Alerini

Lambaré

Baina³

et al. 2008

Geophysical Prospecting

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A B S T R A C TIt has been shown on an 'ideal' synthetic dataset that PP/PS-stereotomography can estimate an accurate velocity model without any pairing of PP-and PS-events. The P-wave velocity model is first estimated using PP data and then, fixing this velocity field, the S-wave velocity is estimated using the PS data. This method needed to be evaluated further and we present here the first application of PP/PS-stereotomography to a real dataset: the 2D East-West Mahogany OBC line (Gulf of Mexico). We are here confronted with data which do not fit our working assumptions: coherent noise (due to an approximate separation of PP-and PS-events and some remaining multiples), probably some anisotropy and 3D effects. With a careful selection of the stereotomographic picks, which allows one to decrease the effect of the picked coherent noise by the automatic picker, our application can demonstrate the relevance of our approach in the upper part of the profile, where anisotropy and 3D effects might be low. We can thus estimate, without any pairing of PP-and PS-events, a velocity field which provides not only flat common image gathers, but also PP-and PS-depth migrated images located at the same positions. For the deeper part of the profile, a significant shift in depth appears. In addition to possible anisotropy, 3D effects and a more complex velocity field ('salt body'), this is due to the quality of the PZ-and X-components profiles: The PZ-component profile where the PP-stereotomographic picking is performed, is polluted by conflicting converted or multiple events and the X-component profile, where the PS-stereotomographic picking is performed, is highly noisy. This study emphasizes the need to develop accurate selection criteria for the stereotomographic picks. I N T R O D U C T I O NThe use of converted waves in reflection seismic imaging can be a significant improvement. Indeed P-and S-reflected waves bear complementary information about the elastic properties of the medium. It concerns both the reference velocity model (P-and S-wave velocities) and the short wavelength components of the elastic parameters describing the model (reflectivity).

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“…Concerning the velocity macromodel, the estimation of depth consistent P ‐ and S ‐wave velocity models requires the identification of some key reflectors among the PP ‐ and PS ‐arrivals. This pairing is fastidious and can be extremely difficult in regions with a poor signal‐to‐noise ratio (Stopin 2001; Broto et al 2003; Foss et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Two-dimensionalPP/PS-stereotomography:P- andS-waves velocities estimation from OBC data

Alerini

Lambaré

Baina³

et al. 2007

Geophysical Journal International

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S U M M A R YWe present the extension of stereotomography to P-and S-wave velocity estimation from PP-and PS-reflected/diffracted waves. In this new context, we greatly benefit from the use of locally coherent events by stereotomography. In particular, when applied to S-wave velocity estimation from PS-data, no pairing of PP-and PS-events is a priori required. In our procedure the P-wave velocity model is obtained first using stereotomography on PP-arrivals. Then the S-wave velocity model is obtained using PS-stereotomography on PS-arrivals fixing the Pwave velocity model. We present an application to an 'ideal' synthetic data set demonstrating the relevance of the approach, which allows us to recover depth consistent P-and S-waves velocity models even if no pairing of PP-and PS-events is introduced. Finally, results to a real data set from the Gulf of Mexico are presented demonstrating the potential of the method in a noisy data context.

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Anisotropic traveltime tomography for depth consistent imaging of PP and PS data

Cited by 21 publications

References 0 publications

Constrained optimization in seismic reflection tomography: a Gauss-Newton augmented Lagrangian approach

Constrained optimization in seismic reflection tomography: a Gauss-Newton augmented Lagrangian approach

2D PP/PS‐stereotomography: Application to a real 2D‐OBC dataset

Two-dimensionalPP/PS-stereotomography:P- andS-waves velocities estimation from OBC data

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