RAEG2003

Amplitude Preserving - CFP Migration as a Tool for AVA Analysis

Abd Haris, Dirk Klaeschen and Ernst Flueh

GEOMAR, Research Center for Marine Geosciences, Germany.

Abstract

We present an Amplitude-Preserving (AP) migration method to estimate angle-averaged reflectivity and angle-dependent reflectivity information from surface seismic reflection data, which is the basis to perform Amplitude Versus Angle (AVA) analysis. Our strategy combines the Common Focus Point (CFP) technique for removing wave field propagation effects with the application of a weight function for preserving amplitudes during the migration process. The method has been developed as a separate program from modeling algorithms by requiring migration operators in the form of seismograms as so-called seismogram operators. Thus, it can be implemented using any kind of migration operators (e.g., single-valued or multi-valued operators), which may be obtained from the existing modeling algorithms. In principle, the AP migration is performed in two complex cross-correlation steps instead of conventional move-out correction. All required quantities (i.e., traveltime, amplitude, phase, and incidence angle) for the amplitude preserving weight function are estimated directly from the seismogram operator itself. According to the realistic modeling, the migration operators are calculated using the Nichols' method so-called band limited Green's function, which is modified for generating multi-valued seismogram operators.

A migration example on a simple generic model is used to verify the developed method and to analyize its subsequent steps and performance. The picked amplitude of the AP migration image shows a good agreement with theoretical reflection coefficients calculated using Zoeppritz' equations. In an application to a real seismic data set, the AP migration has successfully imaged a bottom simulating reflector (BSR), which is associated with the gas hydrate stability zone (GHSZ). The AP migration results in angle-dependent reflectivity gathers as well as a structural image.

raeg2003@tansa.kumst.kyoto-u.ac.jp

Last modified: Sat Nov 16 02:44:54 2002