Garlock Fault

Garlock Fault
Name	Garlock Fault
Location	Mojave Desert, California, United States
Type	Left-lateral strike-slip
Length	~250 km
Coordinates	35°N 117°W

Garlock Fault The Garlock Fault is a major left-lateral strike-slip fault in the Mojave Desert of Southern California that forms a boundary between the Sierra Nevada and the Mojave Block. It extends roughly from the Tehachapi Mountains near Bakersfield across northwestern Kern County to the vicinity of the Death Valley region adjacent to the Panamint Range, influencing topography, drainage, and seismicity across regions near Ridgecrest, Lancaster, and the Antelope Valley.

Overview

The fault traverses terrain associated with the Sierra Nevada, Tehachapi Mountains, Mojave Desert, and Death Valley, and lies near Bakersfield, California, Ridgecrest, California, Mojave National Preserve, Antelope Valley, Searles Valley, and Panamint Valley. It juxtaposes crustal blocks near Tehachapi Pass, Scodie Mountains, and the Owens Valley margin, and connects tectonically to systems influencing the San Andreas Fault, Eastern California Shear Zone, Whittier Fault, and Little Lake Fault. The Garlock links physiographically to basins such as Kern River Valley, Walker Pass, and El Paso Mountains while influencing infrastructure corridors like California State Route 58 and energy developments near Fossil Ridge and Randsburg.

Geology and Structure

Geologic mapping documents the Garlock Fault cutting Mesozoic plutons of the Sierra Nevada batholith, Cenozoic volcanic deposits in the Coso Volcanic Field, and Neogene basin-fill sediments in Mojave Desert basins. It juxtaposes metamorphic complexes of the Kern Canyon Fault zone against Quaternary alluvium near Owens Lake and controls the margin between the Sierra Nevada microplate and the Mojave Block. Structural studies identify anastomosing strands, restraining bends adjacent to the El Paso Mountains, en echelon arrays near Fort Irwin, and splays linking to the Garlock-Hosgri transfer zone analogues; mapped lithologies include granodiorite, gneiss, and Miocene tuffs similar to those in the Cerro Gordo Formation.

Tectonic Setting and Slip Behavior

Tectonically, the Garlock occupies a left-lateral kinematic role accommodating motion between the right-lateral San Andreas Fault system and the extensional Basin and Range Province. Geodetic analyses using Global Positioning System networks, Interferometric Synthetic Aperture Radar, and campaign leveling connect slip rates to deformation across the Eastern California Shear Zone and the Walker Lane belt. Slip behavior is characterized by long-term rates estimated from geomorphology and trenching, interaction with the Mojave Desert seismic belt, and episodic creep or seismic rupture influenced by stress transfer from large events on faults such as the 1992 Landers earthquake, 1994 Northridge earthquake, and the 2019 Ridgecrest earthquakes. Models incorporating viscoelastic response of the crust and coupling to the Pacific Plate–North American Plate boundary illustrate how slip on the Garlock evolves through seismic cycles.

Seismic History and Paleoseismology

Paleoseismic trenches and offset geomorphic markers reveal multiple late Quaternary surface ruptures and earthquake recurrence on the Garlock. Studies correlate scarps, alluvial fan offsets, and radiocarbon ages to events that may have occurred in the Holocene and late Pleistocene, with comparisons drawn to rupture histories on the San Andreas Fault, White Wolf Fault, and the Cedar Mountain Fault. Historical seismicity catalogs include felt events near Ridgecrest, Tehachapi, and Searles Valley; seismological analyses employ waveform inversions, focal mechanisms, and aftershock distributions similar to methods used for San Fernando earthquake and Northridge earthquake research. Paleomagnetic studies and cosmogenic nuclide dating in basins like Searles Lake help constrain slip rates and timing, while turbidite records in nearby basins provide regional seismic context analogous to reconstructions for the Alpine Fault and Queen Charlotte Fault.

Hazard Assessment and Risk Mitigation

Hazard assessments integrate geologic mapping, paleoseismology, geodesy, and seismic hazard models such as those used by the United States Geological Survey and regional planning agencies in Kern County, Inyo County, and Los Angeles County. The fault’s potential to generate significant earthquakes influences building codes adopted in California Building Standards Code updates, emergency plans for communities like Ridgecrest, California and Tehachapi, California, and infrastructure resilience for corridors like Interstate 15 and California State Route 14. Risk mitigation measures reference retrofitting programs administered by Federal Emergency Management Agency, lifeline assessments used by California Office of Emergency Services, and land-use policies in Antelope Valley and Mojave National Preserve. Scenario modeling examines cascading hazards including landslides in the Sierra Nevada foothills, groundwater perturbation near Owens Valley, and effects on energy facilities at Kern County oil fields.

Monitoring and Research Studies

Monitoring employs seismic networks such as the Southern California Seismic Network, borehole instruments affiliated with the EarthScope and USArray initiatives, continuous GPS stations operated by the Plate Boundary Observatory, and InSAR observations from missions like Sentinel-1 and Landsat. Ongoing research includes multidisciplinary projects from institutions such as California Institute of Technology, United States Geological Survey, University of California, Los Angeles, University of California, Berkeley, and Scripps Institution of Oceanography focusing on fault interactions, rupture dynamics, and seismic hazard modeling. Collaborative efforts with agencies like National Science Foundation and data repositories like the Incorporated Research Institutions for Seismology facilitate studies comparing Garlock behavior to other complex faults including the Alpine Fault, Denali Fault, and Hayward Fault.

Category:Seismic faults of California Category:Strike-slip faults