Joint estimation of AVO and kinematic parameters

Conventional amplitude‐versus‐offset (AVO) analysis such as linear fitting of isotime samples after NMO correction does not give reliable results in the presence of interfering reflections or velocity errors. For this reason we propose a new method that is able to remove interference effects on the AVO of the target reflection and minimize the effects of residual moveout. The method is based on the minimization of the difference between observed data and a model that includes theoretical descriptions of the AVO and traveltimes. This minimization is carried out jointly with respect to AVO and kinematic parameters (velocities and traveltimes) and requires the a priori knowledge of the propagating wavelet. The kinematic parameters are given by the NMO equation extended to the fourth‐order term and the AVO is described as a linear combination of a set of orthogonal functions. The AVO functions are derived from a statistical model of reflection amplitude in the presence of velocity error.

Applications to synthetic and real data demonstrate the ability of the method to attenuate distortion effects on the AVO of the primary reflection by interfering coherent noise. The real data example pertains to a marine case where the primary event is contaminated by multiple reflections generated in the water layer and by another event, reflected from an interface deeper than the target, that merges with the examined reflections at the far‐offsets. This causes a subtle tuning that distorts the AVO of the target. Our method attenuates the effects of the multiples and discriminates the ‘double event’ nature of the target reflection at the far‐offsets.