Cedar Mountain Fault

Cedar Mountain Fault
Name	Cedar Mountain Fault
Location	Utah, United States
Type	Normal / strike-slip (complex)
Length	~50 km
Coordinates	39°N 112°W
Region	Basin and Range Province

Cedar Mountain Fault The Cedar Mountain Fault is a Quaternary-aged fault system in western Utah, United States, cutting across the eastern margin of the Great Basin and the western edge of the Colorado Plateau near Cedar Mountain and adjacent basins. The structure links Neogene basin-and-range extension with older Laramide and Sevier structures, influencing drainage networks, alluvial fans, and mineral occurrences in Juab County and nearby Tooele County. The fault has been the subject of mapping by state geological surveys, university research groups, and federal agencies concerned with seismic hazard and groundwater resources.

Geology

The fault transects sedimentary and igneous terranes including exposed sections of the Mesozoic Cretaceous stratigraphy, Paleozoic carbonate platforms mapped in regional studies, and localized Tertiary volcanic rocks associated with Neogene extension. Stratigraphic relations across the fault juxtapose Tertiary basin-fill deposits and Quaternary alluvium against uplifted blocks containing Mancos Shale equivalents and Pennsylvanian–Permian limestones correlated with regional mapping by the United States Geological Survey. Hydrothermal alteration and vein mineralization have been documented in proximate ranges, paralleling mineral occurrences recognized during 19th-century exploration and the Utah Territory mining booms. Sediment provenance studies link detrital packages to headwater catchments in the Oquirrh Mountains and adjoining ranges.

Tectonic Setting and Structure

The Cedar Mountain Fault lies within the Basin and Range Province and forms part of the complex transition to the Colorado Plateau uplift and the high-standing Wasatch Fault Zone system. Structural analyses show mixed normal and right-lateral strike-slip kinematics reflective of oblique extension driven by plate-boundary forces associated with the Pacific–North American plate interaction and intra-continental deformation related to the Rio Grande Rift and broader Neogene transtensional regimes. Cross-cutting relations, fault scarps, and mapped splays indicate an en echelon arrangement with discrete segments, stepover zones, and transfer faults comparable to structures documented along the Sevier Desert Detachment and other Basin and Range faults. Geophysical surveys, including gravity and seismic reflection profiles, have imaged basin geometry and the down-dip extent of fault planes.

Seismicity and Paleoseismology

Instrumental seismicity near the fault is low-to-moderate, with background microseismicity recorded by regional networks operated by the University of Utah Seismograph Stations and the United States Geological Survey earthquake monitoring programs. Paleoseismic trenching studies across scarps have recovered stratigraphic evidence for multiple Holocene surface-rupturing events, enabling luminescence and radiocarbon age constraints correlated with regional paleoearthquake chronologies developed for the Wasatch Front and other western Utah faults. Slip-rate estimates derived from geomorphic offsets and dating place recurrence intervals within the range documented for active Basin and Range faults studied in Nevada and Utah, informing probabilistic seismic-hazard models prepared by the Nevada Seismological Laboratory and state seismic-hazard assessments.

Geomorphology and Surface Expression

The fault produces distinctive geomorphic features including linear escarpments, offset alluvial-fan surfaces, shutter ridges, and beheaded channels visible in aerial imagery and mapped using Landsat and high-resolution LiDAR datasets. Holocene scarps dissect Quaternary deposits and control drainage development that influences tributaries feeding the Sevier River drainage network and closed basins typical of the Great Basin hydrology. Desert pavements, wind-blown loess veneers, and localized pediment surfaces record post-faulting landscape evolution consistent with climatic shifts tied to Pleistocene glacial–interglacial cycles explored by paleoclimatic research at institutions like Brigham Young University and the University of Utah.

History of Investigation

Geologic reconnaissance of the region dates to territorial surveys and 19th-century explorers associated with the Mormon pioneer era and early mining campaigns; systematic mapping and structural interpretation advanced through 20th-century work by the United States Geological Survey and state geological surveys. Academic investigations by faculty and graduate students at Utah State University and University of Utah produced detailed stratigraphic correlations, paleoseismic trench logs, and geochronologic datasets. Collaborative projects with the National Science Foundation and state agencies have funded modern geodetic campaigns using GPS and InSAR to measure contemporary deformation across the fault zone.

Hazards and Risk Assessment

Seismic hazard analyses incorporate the fault into regional fault databases used by the Federal Emergency Management Agency and state emergency management authorities when evaluating shaking potential for population centers, critical infrastructure corridors such as Interstate 80 and local transmission lines, and water-supply facilities serving municipal users. Probabilistic assessments combine slip-rate, recurrence interval, and maximum-magnitude estimates with site-amplification models employed in building-code applications and retrofit prioritization undertaken by local county planners and the Utah Division of Emergency Management. Secondary hazards include surface rupture, slope failure, and sediment redistribution affecting alluvial aquifers and urbanizing valleys.

Economic and Environmental Impact

The fault influences mineral exploration targets, groundwater recharge zones, and the distribution of gravel and aggregate resources used in regional construction, informing decisions by mining companies and county planners involved in land-use permitting. Changes in catchment connectivity impact water rights and irrigation infrastructure central to agricultural stakeholders in Juab and Tooele counties, as overseen by state water-resource agencies and local irrigation districts. Environmental considerations intersect with habitat management for species monitored under state conservation programs and federal statutes administered by agencies such as the United States Fish and Wildlife Service and the Bureau of Land Management.

Category:Geology of Utah Category:Seismic faults of the United States