Characteristics of the Free Surface Multiple Attenuation Using Wave Field Extrapolation

Ferreira, Patrícia P.¹
 Cetale Santos, Marco Antonio²
 Landau, Luiz¹

An important task in seismic data processing is the identification and subsequent suppression of multiple reflections so as to avoid false interpretations about the true subsurface characteristics. A strategy for the prediction and elimination/attenuation of ocean-bottom multiple energy on synthetic marine seismic data is exploited. The methodology proposed for the multiple attenuation is based on forward wave field extrapolation theoretical principles in which the one-way Rayleigh integral uses the input data as a prediction operator by extrapolating its reflections (primaries and multiples) forward in time. The predicted multiples have its amplitudes compared with the input data in order to be adaptively filtered by the application of a program from the Seismic Unix package called Sushape. After the filtering process the estimated multiples are then subtracted from the input data. Instead of using the Kirchhoff summation process, it was employed wave plane shots for the prediction step in order to diminish computational costs. The highlight of wavefield prediction and subtraction process over other methods is the ability in suppressing multiples that interfere with primaries signals without coincidentally attenuating the primaries when the water bottom is either flat or irregular (dip). This work analyses the reliability of forward acoustic wave field extrapolation in the multiple reflection prediction. The effectiveness and possible issues of this scheme in suppressing multiples are described and discussed for two different synthetic velocity models.