SCEC Award Number 13106 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Pinon Flat Observatory: Continuous Monitoring of Crustal Deformation
Investigator(s)
Name Organization
Frank Wyatt University of California, San Diego Duncan Agnew University of California, San Diego
Other Participants
SCEC Priorities 2, 1, 5 SCEC Groups Geodesy, Transient Detection
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 The crustal deformation measurements at Pinon Flat Observatory (PFO), as with the strain measurements we make at other sites, provide data on otherwise unobservable deformation changes and the fault processes that produce them. The period following the 2010 El-Mayor/Cucapah earthquake has shown especially interesting signals, which we attribute to triggered aseismic slip on the San Jacinto fault: initially (over the first 50 days after the mainshock) the equivalent of a magnitude 5.6 event 15 km deep at the south end of the Anza seismic gap, in the same location as the postulated source of aseismic slip after the 2005 Anza earthquake. A subsequent strain episode, from October 2010 through October 2011, can be explained by aseismic slip equivalent to a magnitude 5.8 event at the location of the 2005 earthquake. In March 2013 we observed significant aseismic slip following a magnitude 4.7 event in the Anza region, 15 km to the south of PFO. A review of earlier data shows that similar episodes of rapid aseismic slip occurred following local earthquakes in 2010, 2005, 2001, 1999, and 1992.
Intellectual Merit Merit
Merit:

The crustal deformation measurements at Pinon Flat Observatory (PFO), improve our understanding of crustal deformation over timespans from hours to years, including coseismic, postseismic, and interseismic changes, and gives an unmatched sensitivity for detecting slip on the San Andreas and San Jacinto faults, with a unique basis for identifying and evaluating new signals.
Broader Impacts Impacts:

PFO provides a shared facility for the development of new technologies and new measurements: in the past year new rotational seismometers and fiber strainmeters.
Exemplary Figure Figure 4. Strain-rate changes observed at PFO immediately following the March 2013 Toro Peak earthquake. The PBO borehole strainmeter (BSM) is located inside the area enclosed by the laser strainmeters (LSM's), but the systems are completely independent. The BSM and LSM's show nearly identical increases in the fault-parallel shear strain following the earthquake, with little areal strain.