Modeling and inversion of PS-wave moveout asymmetry for tilted TI media: Part 2: Dipping TTI layer

Show simple item record Dewangan, P. Tsvankin, I. 2007-04-13T07:23:32Z 2007-04-13T07:23:32Z 2006
dc.identifier.citation Geophysics, vol.71(4), D123-D134pp.
dc.description.abstract Dipping transversely isotropic layers with a tilted symmetry axis (TTI media) cause serious imaging problems in fold-and-thrust belts and near salt domes. The modified PP + PS = SS method introduced in Part 1 is applied to the inversion of longoffset PP and PS reflection data for the parameters of a TTI layer with the symmetry axis orthogonal to the bedding. The inversion algorithm combines the time- and offset-asymmetry attributes of the PSV-wave with the hyperbolic PP- and SS-wave moveout in the symmetry-axis plane (i.e., the vertical plane that contains the symmetry axis). The weak-anisotropy approximations for the moveout-asymmetry attributes, verified by numerical analysis, indicate that small-offset (leading) terms do not contain independent information for the inversion. Therefore, the parameter-estimation algorithm relies on PS data recorded at large offsets (the offset-to-depth ratio has to reach at least two), which makes the results generally less stable than those for a horizontal TTI layer in Part1. The least-resolved parameter is Thomsen’s coefficient epsilon that does not directly influence the moveout of either pure or converted modes. Still, the contribution of the PS-wave asymmetry attributes helps to constrain the TTI model for large tilts v of the symmetry axis (v is greater than 40 degrees). The accuracy of the inversion for large tilts can be improved further by using wide-azimuth PP and PS reflections. With high-quality PS data, the inversion remains feasible for moderate tilts (25 degrees is less than v is less than 40 degrees), but it breaks down for models with smaller values of v in which the moveout asymmetry is too weak. The tilt itself and several combinations of the medium parameters (e.g., the ratio of the P- and S-wave velocities in the symmetry direction), however, are well constrained for all symmetry-axis orientations. The results of Parts 1 and 2 show that 2D measurements of the PS-wave asymmetry attributes can be used effectively in anisotropic velocity analysis for TTI media. In addition to providing an improved velocity model for imaging beneath TTI beds, our algorithms yield information for lithology discrimination and structural interpretation.
dc.format.extent 204995 bytes
dc.format.mimetype application/pdf
dc.language.iso en
dc.publisher Society of Exploration Geophysicists
dc.rights ©2006 Society of Exploration Geophysicists. All rights reserved. Authors and publishers may present or republish up to two figures or tables per SEG article or per SEG book without seeking written permission from SEG, provided that full acknowledgment of the source is provided in the new work. SEG considers this fair use. There are no fees associated with this permission. Authors who need documentation that SEG is extending this permission are encouraged to print this message and present it to their publishers. Those who require further documentation should contact the SEG publications director. SEG recommends that authors and publishers who intend to reuse SEG figures or tables also seek consent of the original work’s lead author, if possible. The member search on the SEG Web site might prove a helpful resource in locating these authors. Requests to use any portion of “Seismic Data Analysis: Processing, Inversion, and Interpretation of Seismic Data” should be directed to the SEG publications director.
dc.subject tilted symmetry axis
dc.subject Dipping transversely isotropic layers
dc.title Modeling and inversion of PS-wave moveout asymmetry for tilted TI media: Part 2: Dipping TTI layer
dc.type Journal Article

Files in this item

This item appears in the following Collection(s)

Show simple item record

Search DRS

Advanced Search


My Account