Physical and numerical modeling of an overthrust zone including radial trace profiles and dip moveout processing



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Seismic imaging of complex overthrusts is a very difficult process. The dipping beds and velocity inversions usually result in unsatisfactory resolution of the structure. Work towards improving the image process is necessary and beneficial. Toward this end, a physical and numerical modeling study of an overthrust zone is undertaken. A model was designed and constructed which represents a hypothetical, but realistic, overthrust zone. Model data were collected in a physical modeling tank and processed into a normal moveout stacked section. Numerical zero offset data suggest the presence of the thrust ramp within the data set which was not detected in the NMO section. Radial trace profiles are generated, by a FORTRAN program, within the physical model data set. The radial trace "planes" intersect the midpoint, offset, time data cube at a constant slope of offset versus time. By doing this, diffractions are reduced from fourth order surfaces into simple hyperbolas. The resultant section is a vast improvement over the NMO derived result, and it allows the thrust ramp to be detected. Not only is the result better, but it is a quicker and easier routine than the NMO stack. Finally, the data were dip moveout processed. The diffraction hyperbolas were time converted to attain identical character before DMO was applied, and time corrected following the DM0. The results indicate that dip moveout of radial trace profiles is equivalent to FK migration of these profiles. The radial trace profiles are a superior method of processing data in the overthrust zone.



Seismic waves, Seismic reflection method, Thrust faults (Geology)