SCEC Award Number 17198 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Piñon 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 1e, 2a, 3e SCEC Groups Geodesy, SDOT
Report Due Date 06/15/2018 Date Report Submitted 06/14/2018
Project Abstract
 Crustal deformation measurements at Pinon Flat Observatory (PFO), and at other longbase strainmeter sites not supported by SCEC, provide data on otherwise unobservable deformation changes and the fault processes that produce them. We have identified a repeated pattern of rapid aseismic strain following large local earthquakes in 2001, 2005, and 2013 in the Anza area, as well as after the 1992 Joshua Tree, 1999 Hector Mine, and 2010 2010 El-Mayor/Cucapah earthquakes, though not after the 1987 Superstition Hills or 1992 Landers earthquakes. We attribute this to triggered aseismic slip on the San Jacinto fault at seismogenic depths. We have also (with others) used the longbase laser strainmeters at PFO to elucidate seismic wavefields, by comparing seismic data recorded by them with a local array of seismometers, and with shorter laser strainmeters using optical fibers. We observe departures from the usual models of plane wavefronts, and slightly non-uniform strain, suggesting local site effects even at this geologically homogeneous location.
Intellectual Merit This project continued the operation of the three longbase laser strainmeters (LSM’s) and one fully-anchored long fluid tiltmeter (LFT) at PFO. These systems have provided data that are unique in their quality, completeness, and length, and give an unequalled view of aseismic and seismic deformations throughout the earthquake cycle.
Broader Impacts This effort provides (I) paradigmatic datasets of strain and tilt used for training researchers in this field, or for new areas of research; (II) information on the design and construction of long-base and other sensors for future replication or improvement; and (III) a readily accessible field site that can be used as a training ground for undergraduate and graduate students in a variety of solid-earth studies.
Exemplary Figure Figure 3 of Technical Report. Caption:
Data from late 2008 to the present, for the three LSM’s at PFO. The EW and NWSE are fully anchored, the NS strainmeter is anchored only at one end. The long-term strain trends are compatible with other geodetic measurements. Shaded regions mark times of observed and possible strain fluctuations, some with obvious causes and others not.
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