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

Part of the Chimney Rock fault system, located on the northern San Rafael S well, Utah, was mapped by integrating air photograph interpretation and dif ferential global positioning system (GPS) location data. Fault slip, slip d irections, and hanging wall subsidence/footwall uplift were digitally recor ded in the field along and between the normal faults using Trimble Pathfind er equipment and software. GPS was used to record (with sub-meter precision ) the location of each measurement as well as the UTM coordinates and eleva tion of stratigraphic markers at the top of the Jurassic Navajo Sandstone a nd near the base of the overlying Carmel Formation. The fault system, as we ll 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 lo cations of the major faults. Separations of the selected horizon from the f ootwall to the hanging wall were used to calculate the dip-slip distributio n 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 int ersecting normal faults and the effects of this interaction on slip distrib ution and direction. This project illustrates the complete circle from digi tal mapping to data analysis to numerical modeling to quantitative comparis on of theoretical models and field data. (C) 2001 Elsevier Science Ltd. All rights reserved.