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Preliminary Geomechanical Models of a Basement-Involved Fold in Northern New Mexico.

Tim Ford, Dr. John S. Wickham, and Richard J. McMullen Jr.
Department of Earth and Environmental Science, University of Texas at Arlington

Our numerical geomechanical model for a thrust fault was developed and implemented by the computer program FLAC ver 4.0 to simulate the structural evolution of a basement-involved fault propagation fold undergoing shortening. The numerical solutions are compared to published cross-sections NW of Las Vegas, New Mexico. Although the numerical solutions cannot generate new faults, they do reflect zones of localized plastic failure which might correspond to observed faults in the published cross section. It’s well known in mechanics that distorted elements cause solution algorithms to be¬come unstable. This high distortion of the grid elements causes their collapse and then for the program to crash. (Cardozo and Cuisiat 2008). This problem in FLAC (Itasca 2000) can be overcome by stopping the simulation before the elements collapse and remeshing the grid elements (Itasca 2000). The models show similarities to published cross sections with zones of plastic failure associated with faults on the cross section as well as similar fold geometries. The simulation also has a zone of plastic failure similar to a backthrust that begins at a fault bend in the basement. The cross section does not show a backthrust, but does have a near surface deformation (Medina Syncline) similar to that of the simulation where the plastic failure zone emerges. Future grid convergence/refinement testing will determine the uniqueness and consistency of numerical solutions.

 

AAPG Search and Discovery Article #90152©2012 AAPG Southwest Section Meeting, Fort Worth, Texas, 19-22 May 2012