Thin‐bed AVO effects

Abstract

Tuning caused by closely spaced impedance boundaries affects seismic amplitudes. At zero‐offset the shape of the composite reflected signal approaches the time‐derivative of the original pulse as the layer thickness decreases. For layers thinner than half of the tuning thickness, the reflected amplitude is modified by a factor equal to twice the time‐thickness of the thin layer. Offset‐dependent tuning can be approximated by the time differences between primary reflections. For high‐velocity contrasts locally converted waves will also affect the total reflected seismic response. The contribution from intrabed multiples can, in most cases, be ignored. Correction for offset‐dependent tuning should be considered before conventional AVO analysis.