SCEC Award Number 14215 View PDF
Proposal Category Collaborative Proposal (Special Fault Study Area)
Proposal Title Collaborative Research: Modeling Crustal Deformation in and around San Gorgonio Pass
Investigator(s)
Name Organization
Sally McGill California State University, San Bernardino Richard Bennett University of Arizona
Other Participants Joshua Spinler, Ph.D. student at University of Arizona. We also plan to involve 2 SCEC interns, 4-6 CSUSB undergraduates supported by another grant, 1-2 CSUSB undergraduates supported by this proposal, 1-2 undergraduates from University of Arizona, and 6-8 high school teachers supported by another grant.
SCEC Priorities 4a, 1d, 1a SCEC Groups Geodesy, SDOT, SoSAFE
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 We have contributed significant new crustal motion data for the San Gorgonio Pass Special Fault Study Area, and have begun elastic modeling of fault slip rates in this region. Mature velocities for 41 sites in the San Bernardino Mountains network have now been published, based on NSF- and SCEC-funded work from 2002-2014 (McGill et al., 2015, JGR). The Rinex files for these sites and for sites in the Joshua Tree network (2005-2013) have been contributed to the SCEC Community Geodetic Model compilation. One dimensional modeling of the velocities from the San Bernardino Mountains network yields a rate for the San Bernardino strand of the San Andreas fault (6.5 ± 3.6 mm/yr) that is consistent with recently published latest Quaternary rates at the 95% confidence level, and is slower than our rate for the San Jacinto fault (14.1 ± 2.9 mm/yr) (McGill et al., 2015). During 2013 and 2014 we began collecting GPS data at 23 sites within San Gorgonio Pass, in the gap between the San Bernardino Mountains and Joshua Tree networks. These sites have not been occupied 2-6 times over an 20-month period. Preliminary velocities are available but still have large uncertainties. After third year of occupations in 2015, these new velocities will densify the Community Geodetic Model within the San Gorgonio Pass Special Fault Study Area.
Intellectual Merit We have contributed significant new crustal motion data for the San Gorgonio Pass Special Fault Study Area, and have begun elastic block modeling of fault slip rates in this region. Mature velocities for 41 sites in CSUSB’s San Bernardino Mountains network have now been published, based on NSF- and SCEC-funded work from 2002-2014 (McGill et al., 2015). The Rinex files for these sites have been contributed to the SCEC Community Geodetic Model compilation. One dimensional modeling of the velocities from the San Bernardino Mountains network yields a rate for the San Bernardino strand of the San Andreas fault (6.5 ± 3.6 mm/yr) that is consistent with recently published latest Quaternary rates at the 95% confidence level, and is slower than our rate for the San Jacinto fault (14.1 ± 2.9 mm/yr) (SCEC Science Objective 1a). During summer and fall 2014 we collected over 3200 hours of GPS data, reoccupying 40 sites, including 23 new sites (first observed in 2013) in and around San Gorgonio Pass where velocities were previously. These new velocities will densify the Community Geodetic Model (SCEC Science Objective 1d) within the San Gorgonio Pass Special Fault Study Area (SCEC Science Objective 4a).
Broader Impacts Participants in the summer 2014 San Bernardino Mountains data collection campaign included four SCEC interns (from Smith College, Carleton College, USC and Cal State Los Angeles) and six CSUSB students funded by SCEC. Two of these students are using the GPS data collected for their senior research projects. Also participating were seven CSUSB freshmen and sophomores supported by a grant from the NSF Mathematics Division’s program for Proactive Recruitment in Introductory Science and Mathematics (PRISM). A third set of participants included 8 high school and middle school science teachers. All travel and stipend support for the teachers was covered by a NASA Insight grant on which Dr. Robert DeGroot is a co-PI. As usual, educational activities provided for participants included a field trip to active faults in the region as well as workshops that introduced the scientific goals of the project, that provided training in the operation of geodetic-quality GPS receivers and antennae, that allowed participants to plot time series for the stations that they occupied and to infer fault slip rates by conducting one-dimensional elastic modeling of the site velocities. This work resulted in poster presentations at the 2014 SCEC meeting by my SCEC interns (Thompson et al., 2014) and by the high school and middle school teachers involved in the project (Kline et al., 2014; Vargas et al., 2014)
Exemplary Figure Figure 2: GPS sites within the San Gorgonio Pass Special Fault Study Area. Black squares show existing benchmarks that were observed with SCEC funding during summer 2013 through winter 2015. Black vectors show preliminary velocities using observations up through summer 2014. Uncertainties are still large, and vector orientations for some of the new sites are still anomalous, but the velocity field for the new sites is already more coherent than in our 2013 annual report and will continue to improve with additional occupations planned for spring, summer and fall of 2015 and with inclusion of observations from fall 2014 and winter 2015 that have not yet been processed. (Figure credit: McGill et al., 2015, JGR).