Schuman Wu, Robert Ratliff, Peter Geiser, Roy Kligfield
Computer programs have made seismic interpretation validation a relatively easy and essential task for exploration/production geologists and geophysicists. Interpretation validation for contractional or extensional terranes is generally done by a restoration process using either a flexural slip algorithm, in which both bed-lengths and unit areas are preserved, or a vertical/oblique slip algorithm, in which only unit areas are conserved. The restoration procedure can reveal problems in a seismic interpretation by unreasonable undeformed state geometries; corrections are usually done by modifying the deformed state interpretation, followed by another restoration. This iteration is repeated until a satisfactory result is obtained.
Two useful alternative approaches to iterative restoration are fault prediction and fold modeling. Whereas lithological boundaries are usually well-imaged on seismic profiles, the location of fault discontinuities can be very imprecise. Fault prediction utilizes the deformed and assumed pre-faulting geometry of one or more hanging wall horizons and the connecting fault segment to predict the remainder of the fault geometry. In contrast, fold modeling uses a known or assumed fault trajectory to generate a kinematically valid hanging wall fold interpretation. Depending on the nature of the problem, either flexural slip or vertical/oblique slip can be used for fault prediction and fold modeling. Seismic interpretation using fault prediction and/or fold modeling can quickly generate a via le cross section without using the iterative restoration process.
An example of fault prediction and fold modeling using flexural-slip is presented for a seismic profile from the southern Appalachian fold-thrust belt. A series of seismic profiles across a Cenozoic basin in Northern China are used to extrapolate a 3D fault trajectory using vertical-slip fault prediction; the fault interpretation and incremental deformation patterns predicted by fold modeling are corroborated by recent seismic event data.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994