JOINT ESTIMATION OF AVO AND KINEMATIC PARAMETERS

Conventional amplitude-versus-offset (AVO) analysis such as linear fit ting of isotime samples after NMO correction does not give reliable re sults in the presence of interfering reflections or velocity errors. F or this reason we propose a new method that is able to remove interfer ence effects on the AVO of the target reflection and minimize the effe cts of residual moveout. The method is based on the minimization of th e difference between observed data and a model that includes theoretic al descriptions of the AVO and traveltimes. This minimization is carri ed out jointly with respect to AVO and kinematic parameters (velocitie s and traveltimes) and requires the a priori knowledge of the propagat ing wavelet. The kinematic parameters are given by the NMO equation ex tended to the fourth-order term and the AVO is described as a linear c ombination of a set of orthogonal functions. The AVO functions are der ived 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 contamin ated by multiple reflections generated in the water layer and by anoth er event, reflected from an interface deeper than the target, that mer ges with the examined reflections at the far-offsets. This causes a su btle tuning that distorts the AVO of the target. Our method attenuates the effects of the multiples and discriminates the 'double event' nat ure of the target reflection at the far-offsets.