SCEC Award Number 15007 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Pinon Flat Observatory: Continuous Monitoring of Crustal Deformation
Name Organization
Frank Wyatt University of California, San Diego Duncan Agnew University of California, San Diego
Other Participants
SCEC Priorities 5b, 2c, 1e SCEC Groups Geodesy, Transient Detection, Seismology
Report Due Date 03/15/2016 Date Report Submitted 03/13/2016
Project Abstract
Crustal deformation measurements at Pinon Flat Observatory (PFO), and at other sites not supported by SCEC, provide data on otherwise unobservable deformation changes and the fault processes that produce them. In particular,wehav e 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. Weattribute this to triggered aseismic slip on the San Jacinto fault at seismo-genic depths. Wehav e also observed longer-term strain changes, in particular from October 2010 through October 2011, that can be explained by aseismic slip equivalent to a magnitude 5.8 event at the location of the 2005 earthquake. Recently we have also (with others) using the longbase laser strainmeters at PFO to elucidate seismic wav efields, by comparing seismic data on them with theoretical models, with a local array of seismometers, and with shorter laser strainmeters using optical fibers. Results so far showanum-ber of departures from the usual models of plane wav efronts, and near-uniform strain, suggesting local site effects evenatthis location of uniform geology.
Intellectual Merit This project continues 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 quality, completeness, and length, and give anunequalled viewofaseismic and seismic deformations throughout the earthquakecycle.
Broader Impacts This effort provides (I) paradigmatic datasets of strain and tilt used for training researchers in this field, or for newareas 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 Right Panel of Figure 3 of Technical Report. Caption (from report text):
Tw o comparisons between the directly measured strain rates and and velocities estimated from a local seismic array (by Chen-Ji Lin of TU Mu¨nich), for twoearthquakes with similar directions of arrival. The records showgood agreement for the largest surface wav es, with some attenuation of the highest frequen-cies on the LSM’s – but also, significant disagreements in the longer-period surface wav es, whether in the early part of the wav e train, for the closer event, or the G-wav e pulse for the more distant one.