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The subtraction and filtering methods are two different approaches for
attenuating the noise present in seismic data. These two methods
effectively approximate the covariance operator with a single filter,
for the filtering approach, or a projection filter, for the
subtraction method.
The projection filter seems to improve (1) the conditioning of the Hessian and (2)
the filtering properties of the covariance operator. Therefore,
subtracting the noise might be the method of choice whenever possible.

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Stanford Exploration Project

7/8/2003