HR: 0800h
AN: S41A-0232 [Abstracts]
TI: Super-wide Angle One-way Method and its Applications in Imaging Steep Salt Boundaries
AU: * Jia, X
EM: xjia@pmc.ucsc.edu
AF: Modeling and Imaging Laboratory, Institute of Geophysics and Planetary Physics, University
of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AU: Wu, R
EM: wrs@pmc.ucsc.edu
AF: Modeling and Imaging Laboratory, Institute of Geophysics and Planetary Physics, University
of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, United States
AB:
Although a variety of methods have been proposed to improve the wide-angle accuracy of one-way wave
propagators, the accuracy of wide-angle waves for strong contrast media is still a serious problem and put a
practical limitation on applying these methods to steep reflector imaging.
One-way wave equation has a preferred direction for wave propagation which is either the z-axis or the x-axis in
2D Cartesian coordinate system. For a certain preferred direction, the large-angle waves carry some errors both
in phase and amplitude. However, large-angle waves with respect to z-axis become small-angle waves to x-axis
and vice versa. Based on that, the super-wide angle one-way method has been developed to extend the capability
of one-way propagators by a wavefront reconstruction method which combines and interpolates the two
orthogonally propagated one-way wavefields to rebuild the distorted wavefront to good accuracy.
In this paper, a more complex reconstruction scheme is developed for wave propagation to improve the accuracy
and reduce the artifacts. The new scheme employs the wavefield gradients to determine the weighting function
for the two orthogonally propagated wavefields. We first propagate the wavefield downward completely to get both
the downward wavefield and its gradients. For the horizontal propagator, the wavefield will be obtained by
combining the downward propagated wavefield at each step with the weights calculated from both wavefields.
This scheme can be considered as an intermediate step of the complete wavefront reconstruction.
Numerical examples of impulse response demonstrate the good accuracy of the weighting scheme and the
application in modeling turning waves, compared with the regular one-way method. The large-angle waves can
be modeled correctly. We also show the good performance of this method on imaging the salt dome with
overhanging flanks in the BP 2D benchmark model. The energy has been rebuilt on almost all boundaries of the
salt by this method.
DE: 0545 Modeling (4255)
DE: 0902 Computational methods: seismic
SC: Seismology [S]
MN: 2007 Fall Meeting