MODELING THE SEGMENTED SEVIER NORMAL FAULT: 3D ANALYSIS AND VALIDITY TESTING

The Sevier fault zone near Orderville, Utah, represents a segmented normal fault system within the transition zone between the Basin and Range Province and the Colorado Plateau. In the study area, the Sevier fault consists of three main segments: the Orderville segment, the Spencer Bench segment, and the Mt. Carmel Segment. These three faults accommodate the displacement that a single fault would accommodate in an unsegmented system. The interactions of these normal fault segments led to the development of complex structural geometries exposed along the fault zone. These geometries influence deformation and create fractures that affect expected permeability and fluid flow within the fault zone. Therefore, our analysis of these geometries has implications for groundwater flow, geothermal energy potential, and natural resource extraction within segmented fault systems.

We use the Move2020 modeling suite by Petex to develop a viable 3D model of the complexly-segmented Sevier fault zone based on previously published geologic maps and cross-sections near the city of Orderville in southern Utah. With these data as a base, we digitize geologic layers and fault horizons to build a 3D model of the fault network. We use this model to test the validity of initial cross-sectional interpretations, because earlier researchers’ subsurface interpretations were based on surface mapping rather than direct documentation of subsurface fault and layer geometries. In viable, restorable, 3D models, the cross-sectional lengths of individual layers should remain constant from their initial length to their deformed length. If those lengths are not consistent, then the initial structural interpretation is invalid and we must revise it. To do this, we can change subsurface model characteristics such as fault dip, magnitude of fault displacement, fault shape, spatial relationships between fault segments, or even by adding undocumented blind faults. We hope to answer several research questions through this process: 1) Can we construct a restorable 3D model of the complexly-segmented Sevier normal fault zone? 2) Can we use our model to make transferable interpretations about segmented fault zone evolution? and 3) Based on our model, how do permeability and fluid flow pathways change as a segmented fault zone evolves?