Focusing-effect AVO/AVA: overview of results and assessment of problems

Ioan Vlad

nick@sep.stanford.edu

ABSTRACT

Small-scale heterogeneities in the Earth produce visible focusing of seismic wavefield amplitudes with offset, but minimal variations in traveltimes. These effects are called Focusing-Effect AVO (FEAVO) or AVA (FEAVA) for avoiding confusion with lithology-caused AVO/AVA. FEAVO/FEAVA is not an unpredictable phenomenon that occurs at random. It appears in a number of well-defined geological settings, it can be modeled with appropriate precautions, it can be identified by its spatially predictable patterns, and can be removed in a manner that takes into account the specific physics involved. This paper summarizes work published over the course of several years in seven different SEP reports, providing an overview of the results obtained up to date and an assessment of the most critical problems to be solved.