Computer Models Of A Basement Involved Fault Propagation Fold During The Laramide Orogeny Around Las Vegas, New Mexico

Abstract

Numerical geomechanical modeling is acceptable today for studying geologic structures and is readily accomplished by most computers used by geoscientists and engineers interested in studying geomechanics. Models should be simple so that too many discontinuities are not introduced. This study creates models of a thrust fault, developed and implemented using the computer program FLAC version 4.0 to simulate the structural evolution of a basement-involved fault propagation fold undergoing shortening and then compares them to a published cross section NW of Las Vegas, New Mexico. FLAC is a numerical 2D modeling program for modeling geologic materials and has large strain capability suitable for this type of study. A Mohr-Coulomb plasticity constitutive rule was used with unequal dilation and friction angles for non-associated plastic flow enabling shear band occurrence.Folding is developed with approximately a 300 m crest rise, 880 m bed displacement along the associated thrust fault, and with shear bands producing a backthrust zone located near the Medina Syncline location on the published cross section. Void spaces also occur. Although shear bands might be interpreted as faults, FLAC version 4.0 cannot generate new faults, but the produced uplift was similar to the published cross section and the backthrust creates a surface deformation near to the Medina Syncline. Using the newer version of FLAC version 7.0 could possibly overcome these limitations.