Page 398 - Acquisition and Processing of Marine Seismic Data

7.5 WAVE EQUATION MULTIPLE REJECTION 389

FIG. 7.23 A CDP gather (A) before and (B) after Radon velocity filter (top), and their corresponding autocorrelograms (bot-
tom). Multiples between 500 and 1000 ms in (A) are removed after filtering in (B).

WEMR is a method that models the wave To explain the theoretical basis of WEMR,
field propagated in the water column by a wave let’s assume a seismic signal produced by the
equation modeling approach that considers the seismic source in the water column, reflected
streamer and seafloor geometry. It is accom- from the seabed and recorded at receiver R 3 .
plished in two steps. First, the propagation time The same signal continues its propagation
differences between the multiples are obtained towards the sea surface, where it is reflected
using acoustic wave equation modeling. Second, back towards the seabed. It is then reflected from
the reflection coefficient of the seafloor is esti- the seabed and recorded at the receiver, for
mated. The most important points in suppres- instance, R 6 . Similarly, it is again reflected from
sing the multiples using WEMR are to the sea surface and then the seabed to be
determine the form and the amplitudes of the recorded at receiver R 8 , and the signal propaga-
multiples accurately (Lu et al., 1999). tion continues within the water column in this