SCEC Award Number 11198 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Collaborative Research: Assessing slip rate variations on the Garlock fault using improved OSL sediment dating
Investigator(s)
Name Organization
Edward Rhodes University of California, Los Angeles James Dolan University of Southern California Sally McGill California State University, San Bernardino
Other Participants Belinda Roder, MS student at UCLA;
Lee McAuliffe, PhD student at USC;
2 student field assistants from CSUSB;
Undergraduate student group visits to sites from UCLA & CSUSB
SCEC Priorities A2, A11, C SCEC Groups Geology, EFP, SHRA
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 The aims of this research project were:
i) to assess luminescence dating methods by comparison with an existing high quality radiocarbon chronology from El Paso Peaks (EPP) paleoseismic site,
ii) to develop improved dating approaches, and
iii) to apply these to the site of Christmas Canyon West (CCW), on the central Garlock Fault, in order to provide a fault slip-rate estimate for the last few thousand years.

The project has progressed in a highly successful manner, with significant outcomes so far. This research represents a major step forward towards developing and formally assessing methods to achieve routine reliable luminescence age estimates for paleoseismic and fault slip rate contexts on timescales of 10 years to 100,000 years in Southern California.

Technical science outcomes
• Successful excavation and sample collection at El Paso Peaks paleoseismic site and at Christmas Canyon West,, near Ridgecrest, CA (Garlock fault)
• Investigation of potential of two different K-feldspar IRSL approaches and development of new K-feldspar ITL dating approach showing huge potential
• Exploration of single grain K-feldspar IRSL with encouraging results
• Tentative evidence for increased slip rate for the central Garlock fault over the last 1000 years – preliminary findings require additional research to validate

Training, communication and outreach outcomes
• Two UCLA and one USC graduate students closely involved in research
• Three UCLA undergraduate students participated in research including two female Hispanic students
• Two publications submitted (revisions completed) to peer-reviewed journals
• Six presentations made at international conferences, plus two at SCEC 2011
Intellectual Merit This project contributes by providing the initial research into a method that can be applied at many places around the world to improve our understanding of patterns and timing of fault slip.
Broader Impacts The benefits are first to the academic community, in helping to provide a new tool to improve research findings, secondly in educating researchers and students in specific methods and broader approaches, and thirdly by ultimately leading to improved seismic hazard assessment methods.
Exemplary Figure Figure 3. New Bayesian age model for El Paso Peaks upper central portion comparing new ITL (isothermal thermoluminescence) age determinations with the existing radiocarbon measurements presented by Dawson et al. (2003), following the procedures of Rhodes et al. (2003). The plot clearly illustrates the good age agreement between ITL estimates and C-14 values, although the overall agreement index is rather low at 28.7 %. This is caused by apparent over-estimates for ITL samples J0146 and J0141, but also by C-14 samples EPP-1E-23 and 116, presumably caused by reworking. The ITL over-estimates for these samples probably represent incomplete signal zeroing or thermal transfer effects, and this is the subject of on-going research.