The rank-reduction based methods discussed in this paper deal with a block Hankel matrix (Inline and Xline) in the frequency-space domain. Let
(of size
) represent a 3D seismic dataset. First, we transform
in time-space domain to
in the frequency-space domain. At a given frequency slice, the 2D data can be expressed as (Oropeza and Sacchi, 2011):
(1)
From here on, is omitted for notational convenience. A Hankel matrix is then constructed from
. We first construct a Hankel matrix
as:
(2)
and then construct the block Hankel matrix as:
(3)
Parameters and are chosen to make
and
close to square matrices, e.g.,
and
. The symbol
outputs the integer of an input value. The matrix
is of size , with
, . The block Hankel matrix
is considered to be lowrank (Chen et al., 2019a; Trickett, 2008; Oropeza and Sacchi, 2011; Huang et al., 2016), i.e., it can be approximated by a small number of eigen-images.
Seismic signal enhancement based on the lowrank methods