Velocity-independent $\tau$ -$p$ moveout in a horizontally-layered VTI medium

Published as Geophysics, 76, no. 4, U45-U57, (2011)

Velocity-independent $\tau$ -$p$ moveout in a horizontally-layered VTI medium

Lorenzo Casasanta and Sergey Fomel
formerly: Politecnico di Milano
Piazza Leonardo da Vinci, 32
20133 Milano
Italy
casasanta@elet.polimi.it
presently: CGGVeritas Services
Crompton Way, Manor Royal Estate
Crawley, West Sussex RH10 9QN
UK
lorenzo.casasanta@cggveritas.com
Bureau of Economic Geology,
John A. and Katherine G. Jackson School of Geosciences
The University of Texas at Austin
University Station, Box X
Austin, TX 78713-8972
USA
sergey.fomel@beg.utexas.edu

Abstract:

Local slopes of seismic events carry complete information about the structure of the subsurface. This information is sufficient for accomplishing all time-domain imaging tasks, without the need to estimate or know the seismic velocity model. We develop a velocity-independent $\tau$ -$p$ imaging approach to perform moveout correction in horizontally-layered VTI media. The effective and interval anisotropic parameters turn into data attributes through the use of slopes and become directly mappable to the zero-slope traveltime. The $\tau$ -$p$ transform is the natural domain for anisotropy parameter estimation in layered media, because the phase velocity is given explicitly in terms of $p$ . Therefore, the $\tau$ -$p$ transform allows for reflection-traveltime modeling and inversion that are simpler than traditional methods based on Taylor-series expansions of traveltime in $t$ -$X$ domain. Synthetic and field data tests demonstrate the practical effectiveness of our method.

Velocity-independent $\tau$ -$p$ moveout in a horizontally-layered VTI medium