S. E. Nissen, N. L. Haskell, J. A. Lopez, T. J. Donlon, and
M. S. Bahorich
3-D seismic coherency techniques, which quantitatively measure the similarity or dissimilarity of adjacent seismic traces, have been used successfully to aid in the identification and mapping of a submarine canyon in the South Marsh Island area of the Gulf of Mexico. This canyon is interpreted to be a slump feature, since it contains seismically chaotic fill, with numerous steep-sided blocks, and is similar in shape and size to shelf edge slumps off the modern Mississippi River and to the Late Pleistocene Mississippi Canyon, which was also formed by slumping.
Slump blocks with both high and low seismic amplitudes within the submarine canyon have been delineated using coherency techniques and associated calculations of dip and azimuth of the coherent seismic reflections. Block faces with low amplitude, but relatively high coherence, which are not evident on standard seismic time slices, can be seen on coherency time slices and dip/azimuth plots. These slump blocks produce a distinctive mottled pattern on coherency time slices and correspond to areas of high dip and varied azimuth on dip/azimuth plots. Similar coherency and dip/azimuth patterns are found elsewhere in the world, associated with slumping in areas of faulting, dewatering, and mass wasting.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California