A Model for the Initiation, Evolution, and Controls on Seismic Behavior of the Garlock Fault, California

Abstract

We develop a model for the evolution and activity of the Garlock fault that combines elements of three previously proposed mechanisms: (1) conjugate slip to the San Andreas fault, (2) extension in the Basin and Range, and (3) bending from oblique shear in the eastern California shear zone (ECSZ). Conjugate slip is greatest in the west and decreases eastward. Conversely, extension-induced slip increases westward from the eastern termination of the fault, reaching a maximum at and to the west of the intersection with the Sierra Nevada frontal fault. Oroclinal bending provides only a small contribution to Garlock slip that increases eastward from the east-central segment. These spatiotemporally complex loading patterns may explain alternating periods of fault activity along the Garlock and neighboring faults. Moreover, these complex kinematic relationships demonstrate that the Garlock fault acts as an efficient mechanical bridge linking slip on the northern ECSZ and San Andreas fault that may have delayed or even obviated the long-hypothesized development of a new Pacific-North America plate boundary along the ECSZ-Walker Lane.