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Strain Compatibility Between the Intersecting Airport Lake and Garlock Faults, California

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip II

Type: Oral

Date: 4/22/2021

Presentation Time: 03:00 PM Pacific

Description: 

How dextral shear along the Eastern California shear zone (ECSZ) is sustained across the Garlock fault without apparent cross-cutting geologic relationships remains a long-standing problem in the Cenozoic tectonics of the Mojave Desert that has implications for the mechanical interactions of intersecting fault networks. Our mapping following the 2019 Ridgecrest Earthquake and improved geodetic and seismological perspective from this event gives us clues into how the intersections of dextral strike-slip faults of the ECSZ with the sinistral Garlock fault can be relatively stable and maintain strain compatibility during accumulated deformation. The earthquake sequence along the Airport Lake fault generated surface deformation within 500m of the Garlock fault. Following the event, the Garlock fault saw triggered creep resulting in minor sinistral motion.

The Garlock fault has almost 65 km of total slip and shows rates from 5 to 15 mm/yr. Pliocene strata immediately north of the Garlock fault are displaced ~1.6 km dextrally across the Airport Lake fault, as are Mesozoic basement rocks. This indicates that the time-average slip rate on the Airport Lake fault is likely 1mm/yr or less. Despite the accrued displacement, the Garlock fault trace at the projected intersection appears to be undeformed. These kinematic and geometric relationships suggest a model by which strain passes from the Airport Lake fault to the Garlock fault zone. Airport Lake strain is absorbed by distributed deformation adjacent to the Garlock fault zone by P, R, and R’ shears related to that fault. We suggest that strain accumulates within a broad, up to 1km wide, zone of fault damage and shear parallel to the Garlock fault. This region acts as a compliant buffer zone, into which displacements along ECSZ structures are absorbed. The slip rate difference of nearly a factor of 10 between individual ECSZ structures and the Garlock fault essentially leads to finite strain accumulated along the broad Garlock fault zone that effectively overprints and absorbs deformation on the Airport Lake fault.

Presenting Author: J. Douglas Walker

Student Presenter: No

Authors