SCEC Award Number 12183 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Time-dependent block model for California
Investigator(s)
Name Organization
Robert McCaffrey Portland State University David Sandwell University of California, San Diego
Other Participants
SCEC Priorities 1d, 1e, 5b SCEC Groups Geodesy, WGCEP, CME
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 The purpose of the project was to examine the possibility of using complete GPS time series directly to model the time-dependent deformation of California. We examine the possibility that differences in geodetic and geologic fault slip rates are due in part to the effect that post-seismic motions have on the GPS velocity field. The UCERF3 block model was run with time series of GPS data from the PBO continuous network (2004-2013) and the California campaign GPS time series (1990-2004) obtained from the velocity field CMM4 (Shen et al., 2011). The model comprised the UCERF3 blocks along with 14 earthquakes and afterslip for 8 of them. For the block model, we solved for angular velocity, uniform strain rates, and locking on block-bounding faults. The results were then compared to geologic fault slip rates and to a model that uses linear velocities and InSAR only.
Intellectual Merit The work contributes to the seismic hazard assessment for California by possibly improving fault slip rate estimates from geodetic data to be used in future hazard models. Development of time-dependent inversions will help uncover the long-term motions currently masked by transient signals.
Broader Impacts The work supports the goals of the SCEC Community Geodetic Model (an outgrowth of the Community Stress Model). The software TDEFNODE was improved by this work and is made available freely to researchers (web.pdx.edu/~mccaf/www/defnode). The PI also assists many researchers, including students, in its use.
Exemplary Figure Fig 2. Slip rates and locking depths along the San Andreas and San Jacinto faults from inversion of consensus velocity field and Tong et al. InSAR and GPS times series. In the velocity plots, blue dots are consensus rates and black are predicted. In locking plots, red indicates locked zone and blue is free-slipping and the transition occurs over a 2 km depth range (imposed). The locking models show similarities while the slip rates have some large differences.
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