Digital mapping of three-dimensional structures of the Chimney Rock fault system, central Utah

Abstract

Part of the Chimney Rock fault system, located on the northern San Rafael Swell, Utah, was mapped by integrating air photograph interpretation and differential global positioning system (GPS) location data. Fault slip, slip directions, and hanging wall subsidence/footwall uplift were digitally recorded in the field along and between the normal faults using Trimble PathFinder equipment and software. GPS was used to record (with sub-meter precision) the location of each measurement as well as the UTM coordinates and elevation of stratigraphic markers at the top of the Jurassic Navajo Sandstone and near the base of the overlying Carmel Formation. The fault system, as well as the associated deformation of the sedimentary layers within the fault blocks, have been precisely characterized using this technique. The geographic coordinates and local elevation were transferred to gOcad to produce a three-dimensional surface representation of a selected resistant limestone layer, by interpolating the elevation between the collected data points using imposed constraints such as the dips of the layers and the locations of the major faults. Separations of the selected horizon from the footwall to the hanging wall were used to calculate the dip-slip distribution along the faults. The digital field data were compared with the results of numerical modeling based on continuum mechanics to study the mechanical interaction among intersecting normal faults and the effects of this interaction on slip distribution and direction. This project illustrates the complete circle from digital mapping to data analysis to numerical modeling to quantitative comparison of theoretical models and field data.