THE PARAGONAH FAULT, IRON COUNTY, UTAH: IS ITS REPORTED VERTICAL SLIP RATE VALID?

The Paragonah fault defines the east side of Parowan Valley, Iron County, Utah. It is a poorly exposed, northeast-trending, 27 kilometer-long, west-dipping normal fault. The Paragonah fault has a reported vertical slip rate of 0.46 mm/yr based on a displaced Quaternary (0.44 ± 0.04 Ma) basalt flow. The fault is included in the USGS National Quaternary Fault and Fold Database, where it is categorized as having a slip rate in the range of 0.2-1 millimeter/year. Based upon this comparatively high reported slip rate, the USGS has also included the Paragonah fault on the National Seismic Hazard Maps as a potential seismic source in southwestern Utah. However, the fault's generally subdued geomorphic characteristics, combined with significantly lower slip rates for other similar Quaternary faults in the region have brought this high slip rate into question.