SCEC Award Number 12210 View PDF
Proposal Category Individual Proposal (Special Fault Study Area)
Proposal Title Frequency, Timing and Size of San Gorgonio Pass Fault Zone Ruptures
Investigator(s)
Name Organization
Doug Yule California State University, Northridge
Other Participants
SCEC Priorities 2a, 4a, 4c SCEC Groups Geology, SoSAFE, USR
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 The objective of this project is to lengthen and deepen trenches at the Cabazon paleoseismic site to extend the rupture history of the San Gorgonio Pass fault back ~1500 yrs. Work funded by a 2011 SCEC grant constrained the timing of the most recent rupture at this site occurred to the 14th century. Work funded by SCEC Award #12210 aims to test whether >500-yr recurrence intervals hold for multiple events at this site. This work is significant to help understand the seismic hazard posed by the southern San Andreas fault. Through-going San Andreas Fault rupture (Coachella Valley to Mojave sections, and beyond) may be a relatively rare event if long recurrence periods are supported here in San Gorgonio Pass. Unfortunately, for a variety of unforeseen reasons field work has been postponed until May-June 2013 when the PI and a group of students will focus efforts here. Results will be reported at the Annual SCEC Meeting in September of 2013. Award #12210 has been extended until 1-31-14 and a revised report will be submitted then.
Intellectual Merit This work contributes to the understanding of San Gorgonio Pass, a Special Fault Study Area in SCEC4. This research tests the hypothesis that large San Andreas Fault ruptures continue through the structurally complex San Gorgonio Pass region, as depicted by the 2008 ShakeOut Scenario event and subsequent kinematic, dynamic, and mechanical models. Results will also contribute to an understanding of the 3D structure geometry of faulting here and their representation in UCERF3. Results therefore will impact geologic and geophysical models for the southern San Andreas and will help shape the earthquake forecast models for southern California.
Broader Impacts The PI has incorporated work from this project into two courses: 1) a general education course "Living with Earthquakes in Southern California", and 2) a graduate-level course "Geology of Earthquakes". Two field trips to San Gorgonio Pass (in June and October 2012) visited field sites supported by this work. One trip included SCEC scientists as part of a SCEC-sponsored SPFSA Workshop in June 2012. Another included ~75 members of the South Coast Geological Society in October 2012. The PI continues to work closely with the Morongo Tribe and meets once per yr with the Tribal Council to report on scientific progress related to this work. This work will support one MSc graduate student thesis and one undergraduate student assistant at CSUN.
Exemplary Figure Figure 2. Oblique view of the west wall of T5 at the Cabazon paleoseismic trench site. Units 100-500 consist of interbedded silty mud, fine to coarse sand, pebbly sand, and fine to coarse gravel. A distinct unconformity (U4) identifies the most recent earthquake (note thrust projected to base of U4 at back of trench). A lower unconformity (U3) may record the penultimate event (note thickening of Unit 200 to left of person logging trench).
Linked Publications

Add missing publication or edit citation shown. Enter the SCEC project ID to link publication.