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Group A, Poster #077, Earthquake Geology

Advancements to the Garlock fault incremental slip rate record: an update on ongoing research

Dannielle M. Fougere, James F. Dolan, Ed J. Rhodes, Sally F. McGill, & Andrew Ivester
Poster Image: 

Poster Presentation

2023 SCEC Annual Meeting, Poster #077, SCEC Contribution #12916 VIEW PDF
An expanding catalog of slip rate and paleoearthquake age data reveals that while some major plate-boundary faults experience constant slip behavior (e.g., Alpine fault, New Zealand; North Anatolian fault, Turkey), many others experience non-constant earthquake behavior over multi-millennial scales (e.g., Awatere and Wairau fault, New Zealand; San Andreas fault, Southern California). Temporal variations in strain accumulation and release, and potential system-level fault interactions, complicate seismic hazard assessment in regions with large, mechanically integrated plate-boundary fault systems. Combining records of paleoearthquake ages with incremental fault slip rates over multiple time s...cales from regional fault systems is crucial for developing a better understanding of the underlying mechanisms driving these behaviors.

Here, we present the most up-to-date slip rate and paleoseismic data for the Garlock fault, a major left-lateral strike-slip fault, using lidar- and field-based mapping together with single-grain infrared-stimulated luminescence dating to generate one of the most detailed incremental slip rate records of a major strike-slip fault in Southern California. When added to the available incremental slip rate record, integrating our slip rates and paleoearthquake ages support previous evidence that the Garlock fault has experienced pronounced periods of alternating fast-slow elastic strain energy release over the past ~13 ka, indicated by significant temporal variations in slip rates averaged over multiple earthquake cycles as well as brief periods of earthquake recurrence separated by long periods of seismic quiescence. Specifically, the Garlock fault slip rate has varied by a factor of two to five during the Holocene, where periods of fast slip appear to correlate with bursts of earthquake recurrence. Ultimately, comparisons of paired incremental slip rate and paleoearthquake records with other nearby plate-boundary systems (e.g., the San Andreas fault) will lend insights into the controls of strain accommodation in the upper crust and allow systematic comparisons necessary to fully determine how plate-boundary slip is partitioned amongst major faults in time and space.