SCEC Award Number 19204 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Cajon Pass Earthquake Gate Area: Refining the Cajon Pass Quaternary surfaces chronology ­ implications for the long term slip rates of the San Jacinto and San Andreas systems
Investigator(s)
Name Organization
Paula Figueiredo University of Cincinnati Lewis Owen University of Cincinnati Ray Weldon University of Oregon Nate Onderdonk California State University, Long Beach
Other Participants
SCEC Priorities 1a, 2c, 3a SCEC Groups SAFS, SDOT, Geology
Report Due Date 04/30/2020 Date Report Submitted 04/28/2020
Project Abstract
 The Cajon Pass Earthquake Gate Area initiative aims to recognize how the custal deformation has been distributed in the Cajon Pass Area, and namely to understand how a surface rupture in a given structure can initiate, propagate or stop in an area with several main active faults systems that are likely to interact beetween themselves. To address this question and recognize deformation patterns we want to learn about the Holocene deformation but also quantify and recognize patterns of deformation for a larger period of time. This proposal aims to revisit the surface terraces chronology developed by Weldon (1986) by applying TCN 10Be, 10Be/26Al and 36Cl and OSL geochronology methods in late Pleistocene to Holocene terrace surfaces displaced by both the San Jacinto and the San Andreas fault systems. By obtaining these ages and by improving the measurements of displaced landforms, the slip-rate data will be improved, which will contribute to address questions about partition of deformation, fault interaction and earthquake hazard.
The surfaces targeted were Qoa-d (never measured) and a Qoa-c surface age (never directly measured near the fault, but indirectly estimated), all of them directly displaced by active structures and the offset amounts have been estimated from LiDAR dataset (San Bernardino County and B4).
When ready, the results will be written up for publication and data made available for the scientific community. This proposal addressed directly several SCEC priorities, in particular refining the geologic slip rates on southern California faults.
Intellectual Merit It provides quality data (numerical dating) to advance knowledge regarding long-term slip rate of several branches of SAF and SJF fault systems in the Cajon Pass area, revising a regional chronology that is applied for several fault studies. Once the data is completed it is likely that newer concepts may be developed.
Broader Impacts This project provided to Paula Figueiredo, an Early Career Scientist, Post-doctoral Researcher, the opportunity to study a complex geomorphology situation in a world class location, gaining field and laboratory experience while working with excellent scientists. During the timeframe of this project, Paula Figueiredo had the chance to learn new laboratorial protocols in both TCN and Luminescence, which were applied in the setting up of new laboratories. During 2018 and early 2019, Paula Figueiredo mentored an UC undergraduate Antonio Votor: he participated in the Cajon Pass samples collection and later in the preparation of TCN and OSL samples in the Geochronology Laboratories in UC. The experience motivated him to apply to graduate school. Paula Figueiredo presented much of this project study in invited talks (University of Kentucky) and in the weekly seminar series of the Department of Marine, Earth, and Atmospheric Sciences at NC State in October 2019.
This project is aligned with some work developed by Onderdonk focused on a new slip-rate site on the Glen Helen fault strand, and continued mapping of the Glen Helen and San Jacinto fault strands. The collaboration with Onderdonk and his students has been very positive and most beneficial.
Exemplary Figure Fig.5 – Lytle Creek target area. Terraces Qoa-e in blue and Qoa-d in grey. Location of samples is indicated by stars: blue -already measured (TH-e and DC-e, Texas Hill and Duncan Canyon); yellow TH-d, already collected. Lytle Creek fault trace is indicated. A creek incised into Qoa-d is right lateral displaced about 155m. Thick deposit of TH-e is also illustrated.
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