Group B, Poster #086, Earthquake Geology

Refining the record of incremental slip rate and paleo-earthquake ages for the western and central segments of the Garlock fault

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

Poster Presentation

2022 SCEC Annual Meeting, Poster #086, SCEC Contribution #12014 VIEW PDF
An increasing inventory of paleoseismic data indicate that whereas some faults experience relatively regular earthquake recurrence, many other faults exhibit earthquake recurrence that is highly irregular in both time and space. Moreover, significant changes in the rate of slip have been observed on some faults at a variety of time scales. Documenting detailed strain release patterns using combined records of paleo-earthquake ages and incremental fault slip rates over multiple time scales from regional fault systems is crucial for developing a better understanding of the underlying mechanisms driving these behaviors. However, there are currently too few sites where these paired data are avai...lable to make the systematic comparisons necessary to fully determine how plate-boundary slip is partitioned amongst major faults in time and space. Possible 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. Here, we present two new mid-Holocene slip rates from the Garlock fault from (1) the Clark Wash site, and (2) the Summit Range East site. We use lidar- and field-based mapping together with single-grain infrared-stimulated luminescence dating to calculate these new slip rates. We also present a new paleoearthquake record from the northeastern corner of the Koehn Lake extensional step-over on the western part of the central segment. When added to the available incremental slip rate record, these new slip rates and paleoearthquake ages support previous evidence that the Garlock fault experiences pronounced periods of fast and slow elastic strain energy release over the past ~13 ka, indicated by significant temporal variations in slip rates 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 the paired incremental slip rate and paleoearthquake records with other nearby plate-boundary systems (e.g., the San Andreas fault and the eastern California shear zone) will lend insights into the controls of strain accommodation in the upper crust of this section of the Pacific-North American plate boundary.