SCEC Award Number 18133 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Pinon Flat Observatory: Continuous Monitoring of Crustal Deformation
Investigator(s)
Name Organization
Duncan Agnew University of California, San Diego
Other Participants Frank Wyatt,
Don Elliott,
William Hatfield
SCEC Priorities 1e, 2a, 3e SCEC Groups Geodesy, Seismology, SDOT
Report Due Date 04/30/2020 Date Report Submitted 11/04/2020
Project Abstract
 Crustal deformation measurements at Pinon Flat Observatory (PFO), and at other longbase strainmeter (LSM) sites not supported by SCEC, have provided data on otherwise unobservable deformation changes and the fault processes that produce them. With the ending of funded LSM operation in 2018, we can conclude that, in the strike-slip setting found in most of Southern California, departures from steady strain accumulation during the interseismic period are few and far between.
At PFO we have observed repeated rapid aseismic strain following moderate local earthquakes in 2001, 2005, and 2013 in the Anza area, as well as after the 1992 Joshua Tree, 1999 Hector Mine, and 2010 El-Mayor/Cucapah earthquakes, though not after the 1987 Superstition Hills or 1992 Landers earthquakes: a total of six occurrences over 47 years of operation. At other sites close to the San Andreas fault, we have likewise observed rapid aseismic slip a few times per decade, though in those locations modeling suggests that the signals are caused by shallow creep.
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.
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

Data from late 2008 to summer 2018, 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.