Hydrogeologically important features of fault zones include undamaged country rock, the damage zone, and the core zone. Fault cores generally have low porosity and permeability, and often act as a barrier to groundwater flow. The damage zone, by contrast, consists of small faults and fracture networks, which can act as conduits. Timpoweap Canyon near Hurricane, Utah has superb exposures of the fault core and damage zone of the Hurricane Fault. Also within the canyon, springs discharge from the damage zone into the Virgin River, providing an ideal natural laboratory for the study of groundwater discharge from a fault zone. The Hurricane fault is an active, steeply dipping, normal fault that is 250 km long, and exhibits about 2500 m of displacement. The damage zone in Timpoweap Canyon controls thermal groundwater (~40°C) and CO2 gas discharge from highly fractured limestone. Total spring discharge is 260 L/s. Approximately 4 L/s of CO2 gas also discharges with the springs. The δ^2H and δ^16O composition of the springs exhibits a geothermal shift from the global meteoric waterline. This suggests that the circulation depth is about 3 km below the ground surface (bgs) in basement bedrock. The CO2 gas discharging originates from either magmatic sources or from diagenesis. The fracture density in a typical damage zone decreases with increasing distance from the fault, thus spring discharge should also decrease with increasing distance from the fault. The damage zone in Timpoweap Canyon does not follow this pattern because pre-existing fractures that developed from Laramide and Sevier Orogeny stresses suppress the pattern. Collapse structures from gypsum dissolution and large fractures also control the location of spring discharge.

Spring water inflow is distinct at Pah Tempe Hot Springs (also known as Dixie Hot Springs) situated within the damage zone of the Hurricane Fault in Timpoweap Canyon in Hurricane, Utah. Excising of the footwall by the Virgin River has created Timpoweap Canyon and allowed an unusual opportunity to study the spring inflow in relation to the fault damage zone. While correlation of these springs with the damage zone and visible fracture patterns on the canyon wall has been made, no subsurface faulting has been imaged to verify connection to these visible fractures and spring inflows (Nelson et al., 2009). The stream was logged and contoured to note the varying locations of spring water inflows in contrast with unsaturated Virgin River water. Seismic surveys were conducted and subsurface profiles made to locate offsets and faults. Photogrammetry was conducted and a three-dimensional model of the canyon and cliff wall was created to facilitate remote fracture mapping of this wallSubsurface features correlate to fractures, spring water inflow locations, and surface faults mapped by Biek (2002). This suggests that faulting and fracturing from the Hurricane Fault provides subsurface conduits for these thermal waters to rise. In one area in the stream, thermal inflow correlates with both subsurface offsets and major surface fractures. Numerous correlations between just spring water entry and subsurface offsets or surface fractures are also found. Fracture and fault density is atypical at Pah Tempe as these features do not diminish with distance from the main strand of the fault. This has led to the Sevier Orogeny accounting for creating the observed fracture conduits at Pah Tempe. Fractures in the canyon wall at Pah Tempe open west to east. This is indicative of the maximum horizontal compressive stress of southern Utah being north to south (Zoback and Zoback, 2015). Therefore the spring inflow at Pah Tempe is likely a result of the damage from the Hurricane Fault creating conduits for spring water to rise, rather than the Sevier Orogeny.