Page 374 - Acquisition and Processing of Marine Seismic Data

CHAPTER

7

Suppression of Multiple Reflections

OUTLINE

7.1 CDP Stack 368 7.5 Wave Equation Multiple Rejection 388
7.2 Predictive Deconvolution 372 7.6 f-k Filtering 391
7.3 Deconvolution in τ-p Domain 382 7.7 Surface-Related Multiple Elimination 394

7.4 Radon Velocity Filter 383 7.8 QC in Multiple Suppression 400

Multiple reflections occur when the seismic initiated at the sea surface. The other type is the
signal travels along the same ray path more than short period or interbed multiples, which have
once, commonly within the water column. In their downward reflections initiated at the sea-
marine seismic acquisition, these are generally floor or subsurface interfaces (Dragoset and
referred to as reverberations, and they may Jeric ˇevi c, 1998).In addition to these common mul-
induce significant issues during the processing tiple types, peg-leg multiples, which are reflected
of data collected with short streamers in rela- from a strongly reflective interface in the subsur-
tively shallow waters (Section 3.3). Multiples face, commonly from the acoustic basement, and
are one of the most serious noise problems in then downward reflected from the sea surface,
marine seismic surveys, since they generally can create recurring phantom interfaces that
occur in the frequency band of the primary mimictheactualreflector.Sincetheirfirstrecogni-
reflections and their arrival times generally also tion on the seismic records in the late 1940s,
coincide with those of the primary reflections. considerable efforts have been made on the sup-
Two different types of multiples are observed pression of multiple reflections. The first dedi-
in marine surveys (Fig. 7.1). The first type is cated attempt to attack multiples was inverse
directly related to the sea surface and they are filtering or predictive deconvolution, and several
known as long period or surface-related multi- different techniques were developed later with
ples, whichhaveatleast one downwardreflection different specific assumptions. In this section,

Acquisition and Processing of Marine Seismic Data 365 # 2018 Elsevier Inc. All rights reserved.
https://doi.org/10.1016/B978-0-12-811490-2.00007-4