Geometry and kinematics of active normal faults, South Oquirrh Mountains, Utah: implication for fault growth

摘要: Abstract The NNW-striking South Oquirrh Mountains normal fault zone consists of four individual faults. faults are arranged in a right-stepping pattern the north and left-stepping south, forming convex-shaped map view with apex towards hanging wall. Late Quaternary activity is characterized by 2.0–4.5 m high discontinuous scarps developed both late alluvium bedrock. bedrock contain evidence two large rupture events. last earthquake occurred prior to highstand Bonneville lake cycle (15 ka), based on cross-cutting relationship between shoreline scarp, comparisons scarp morphology. Cumulative displacement patterns inferred from range crest elevations, Bouguer gravity data adjacent basin rotation subsidiary West Mercur similar displacements measured across scarps; that is, maximum near zone, where located, then tapers off ends zone. Fault traces few meters tens kilometers long dominant orientations (strike N11°W N43°W): separated each other statistically constant angle 33° ± 3°. Slip directions concentrate trend S70°W for groups faults, perpendicular average strike These indicate geometry surfaces non-cylindrical may be composed self-similar structural ridges troughs variable wavelength amplitude elongated parallel slip direction. relationships geometry, geomorphology suggests growth model which points sections mark nucleation primary Secondary at step into footwall block as grows laterally. Intersecting regions laterally growing zones concave-shaped view.