FORWARD & INVERSE MODELING OF FAULT-BEND FOLDS FROM INTEGRATED 3D SURFACE DATA

Construction of balanced cross sections from surface data using fault-bend fold equations can be a time-consuming and labor intensive process. We present an approach that utilizes surface data integrated in a 3D environment with forward and inverse modeling for fault-bend folding based on a velocity description of deformation to construct balanced cross sections in an efficient and objective manner. Surface data consisting of contacts, faults and attitudes are integrated into a 3D GIS environment. Curviplanar ribbons constructed from 3D map trace contacts are extended into the shallow subsurface. These 3D subsurface features intersect mutually parallel 2D vertical planes, defining section lines. These contain traces of bedding orientations at contacts extracted from a combination of ribbons and an average of proximal attitudes projected to the contact. Along each section, we create balanced forward models using a kinematic approach constrained by local stratigraphic thicknesses and known detachment levels. We evaluate how well the modeled contacts compare to the known data on the section and iterate to converge on better solutions which minimize the difference between modeled and observed bedding contacts and faults. Multiple forward models are run with different displacement, stratigraphy and fault geometries, either manually, with the user adjusting the parameters after each model, or with an inverse model using a genetic algorithm. We stitch together multiple cross sections, creating a 3D fault-bend fold model, allowing us to rigorously quantify along strike changes in slip and fault geometry. We test our approach on the Sequatchie anticline in NE Tennessee.