3D forward trishear fault propagation folding modeling

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Cardozo, Nestor
Holding Date 23 September 2008

Trishear is a kinematic model of fault propagation folding in which the displacement along the fault is accommodated by heterogeneous shear in a triangular zone radiating from the tip line. Two formulations are available to run the model in 3D: A pseudo-3D formulation in which the 2D model is solved along serial cross-sections all parallel to the slip direction, and a true 3D formulation in which the kinematics is solved in 3D assuming volume conservation. Although ad-hoc, the pseudo-3D formulation preserves volume in simulations without and with lateral fault propagation, and therefore it is adequate to model trishear in 3D.
A disadvantage of the pseudo-3D formulation is that it produces very simple and perhaps not realistic hanging wall geometries, specially in models with variation of fault slip along strike. The true-3D formulation produces more realistic hanging wall geometries, but it contains inconsistencies that result in significant volume changes in models with high fault slip gradient along the tip line. The validity of the pseudo-3D and true-3D algorithms is tested by comparing forward analogue and trishear models of fault propagation folding above reverse, basement-involved faults. 3D trishear forward modeling of the San Rafael Swell in Utah is also presented.