SCEC Award Number 13098 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title SoSAFE- San Jacinto: Extending the Mystic Lake paleoseismic record back to 2000 years along the northern San Jacinto fault zone.
Investigator(s)
Name Organization
Nate Onderdonk California State University, Long Beach Tom Rockwell San Diego State University Sally McGill California State University, San Bernardino
Other Participants At least one graduate student and several undergraduate students and SCEC interns will be involved in the proposed project.
SCEC Priorities 2, 2, 4 SCEC Groups SoSAFE, Geology, WGCEP
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 Paleoseismic trenching at the Mystic Lake site has resulted in a record of 15 earthquakes over the past 3700 years on the Claremont fault, northern San Jacinto fault zone. We believe we have a complete record for the past 2000 years during which there were 11 or 12 earthquakes. Our record for the preceding 1700 years (0 to 1700 BC) only includes 3 or 4 earthquakes and is most likely not complete due to missing stratigraphic section. The recurrence interval for the last 2000 years is between 160 and 190 years, and the last ground rupturing earthquake occurred around 1800 AD. The 214 years that have passed since the last rupture is equal or slightly larger than the longest hiatus between earthquakes in the past 2000 years.
Intellectual Merit This project provides the first record of the timing of pre-historic earthquakes and the first recurrence interval calculation for the past 2000 years on the Claremont segment of the northern San Jacinto fault. Comparison of these data to similar data from adjacent faults (the Mojave section of the San Andreas fault and Clark segment of the San Jacinto fault) suggest some earthquakes on one of these faults results in simultaneous rupture on another fault, or triggers a separate rupture within a few decades on another fault.
Broader Impacts The data generated by this study can be used to refine earthquake hazard analysis for the surrounding communities in the form of probabilities of future large earthquakes. The study also provided research experience to numerous undergraduate and graduate students from three California State University campuses and SCEC interns and was the basis for three Masters theses in the past 5 years.
Exemplary Figure The exemplary figure is located on the first page of the report, separate from the Technical Report. It is also used as Figure 4 in the Technical Report.
Caption for general audience: Comparison of the timing of pre-historic earthquakes recorded at the Wrightwood paleoseismic site on the San Andreas fault, the Mystic Lake site on the Claremont segment of the San Jacinto fault, and the Hog Lake site on the Clark segment of the San Jacinto fault. The timing of earthquakes is represented as probability density functions (colored shapes) and the gray lines indicate possible correlations between sites. These possible correlations suggest some earthquakes may have ruptured across gaps between fault segments or that an earthquake on one fault triggered a closely-timed earthquake on an adjacent fault.