Abstract
Compressional primary seismic nonzero offset reflections are the most essential wavefield attributes used in seismic parameter estimation and imaging. We show how the determination of angle-dependent reflection coefficients can be addressed from identifying such events for arbitrarily curved three-dimensional (3-D) subsurface reflectors below a laterally inhomogeneous layered overburden. More explicitly, we show how the geometrical-spreading factor along a reflected primary ray with offset can be calculated from the identified (i.e., picked) traveltimes of offset primary reflections. Seismic traces in which all primary reflections are corrected with the geometrical-spreading factor are, as is well-known, referred to as true-amplitude traces. They can be constructed without any knowledge of the velocity distribution in the earth model. Apart from possibly finding a direct application in an amplitude-versus-offset (AVO) analysis, the theory developed here can be of use to derive true-amplitude time- and depth-migration methods for various seismic data acquisition configurations, which pursue the aim of performing the wavefield migration (based upon the use of a macro-velocity model) and the AVO analysis in one step.
