SCEC Award Number 15214 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Collaborative Research: Refining the ages of large thrust earthquakes on the Puente Hills and Compton blind thrust faults using newly developed post-IR-IRSL luminescence dating
Investigator(s)
Name Organization
James Dolan University of Southern California Edward Rhodes University of California, Los Angeles
Other Participants John H. Shaw (Harvard)
Thomas L.Pratt (USGS, Reston)
SCEC Priorities 1a, 2a, 4a SCEC Groups Geology, SDOT, WGCEP
Report Due Date 03/15/2016 Date Report Submitted 04/28/2016
Project Abstract
 Because of their proximity to metropolitan Los Angeles and potential for generating large-magnitude events, we must characterize the return periods, temporal regularity, and displacements of faults directly beneath the urban region, such as the Puente Hills and Compton blind thrust faults. Despite enormous progress over the past 20 years in documenting the location, geometry, and slip rates of these faults, the ages of the paleo-earthquakes that they have generated over the past 10,000–12,000 years remain surprisingly poorly constrained. This is not because we have been unable to identify the stratigraphic position of paleo-event horizons, but rather because the scarcity of carbon samples suitable for radiometric dating has prevented us from determining the ages of all strata bracketing the event horizons. We will determine the ages of Holocene-latest Pleistocene earthquakes on the PHT and Compton blind thrusts by using the newly developed, post-IR IRSL225 luminescence chronometer, a dating tool that can date feldspar grains with a resolution approaching that of radiocarbon in many cases. The original graduate student attached to this proposal de-committed on short notice, which has significantly delayed progress on this project. However, graduate student Alex Hatem (USC) will now be taking the lead on this work and will begin the borehole drilling in summer of 2016.
Intellectual Merit This project will help to characterize two of the greatest hazards posed to the Los Angeles metropolitan region by providing timing constraints on the most recent events on the Puente Hills and Compton Hills blind thrust fault. In addition to the obvious societal implications, this project will advance our understanding of possible coordinated slip behavior in regional fault systems (i.e., is there a coordinated earthquake sequence between the San Andreas, Garlock, Eastern California Shear Zone, and PHT/CBT?).
Broader Impacts This project will provide a female graduate student (Alex Hatem, USC) with valuable field experience and training in determining paleo-earthquakes on a blind thrust fault, including: (1) acquiring cores for stratigraphic analysis, and (2) preparation of dating samples for using the newly developed post-IR-IRLS dating tool.
Exemplary Figure Figure 1: Borehole cross section through locus of folding during recent Compton blind thrust fault earthquakes, Stanford Avenue site (Leon et al., 2009). Note folding of constant-thickness sand unit 10 and onlap of unit 8 sand against 1.1-m- tall fold.