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Moveout differences between primary and multiple events are often
used to discriminate primary and multiple energy in a CMP
gather. Examples of methods which rely on moveout differences are
NMO stacking and velocity transforms. NMO stacking can reduce multiple
energy but is undesirable because the gathers cannot be
reconstructed from the stacked traces. Velocity transforms, on the
other hand, are invertible. An invertible transform allow gathers to be
transformed from prestack space into velocity space and then back
to the prestack space.
Also, velocity transforms map primary and multiple energy into two
distinct regions of model space. This allows
the multiple energy to be separated from the primary energy with a
simple masking procedure.
Beam stack transforms, like the velocity
transform, are invertible and map primary and multiple energy from the
gather space into two distinct regions of model spaceBiondi (1990).
Because of these two properties, the beam stacked space
is a good space to identify and remove multiple energy. The beam
stacking operator has additional advantages over velocity transforms.
Unlike the velocity transform, beam stack transforms do not assume a global
shape for events or constant amplitude across the event. Beam stack
transforms simply model the stepout of events while velocity transforms
model hyperbolic or near hyperbolic
events. Because of this, beam stacking transforms are more appropriate
than velocity transforms for the task of modeling data with non-hyperbolic
moveout and AVO.
Next: MULTIPLE SEPARATION THEORY
Up: Holden & Biondi: Multiple
Previous: Holden & Biondi: Multiple
Stanford Exploration Project
11/11/1997