SCEC Award Number 14006 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Time-dependent block and deformation model for California
Name Organization
Robert McCaffrey Portland State University
Other Participants
SCEC Priorities 1d, 1e, 5b SCEC Groups Geodesy, CME, WGCEP
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
The work performed was to extract from continuous and survey-mode GPS timeseries the linear velocities at the sites along with parameters that describe co-seismic slip and afterslip of recent earthquakes (1992-2014). The time series from 550 sites in the CMM4 velocity field (Shen et al., 2011), from ~800 PBO sites and from ~300 sites from the Pacific Northwest velocity field (McCaffrey et al. 2013) were inverted simultaneously to estimate the source parameters for 13 earthquakes and afterslip for 10 of them. The linear velocities estimated were then used in a block model for California and vicinity to estimate slip rates on faults and to test whether or not the method used improves the agreement of the geodetic velocities with the geological slip rates. When the predicted fault slip rates at 13 well-determined locations are constrained to be within 1 mm/yr of the geologic rate, the new CMM4 survey-mode velocities give a normalized rms (Nrms) misfit of about 10% better for the same model and constraints. The improvement may be due to the longer time series providing better representations of the afterslip than was available for the original CMM4 estimates but other factors are likely involved. Eleven of the 13 geologic slip rates agree with the geodetic rates when the geologic rates are allowed to vary by 5 mm/yr.
Intellectual Merit The work contributes to the seismic hazard assessment for California by 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 upon request. The PI also assists many researchers in its use. The PI attended the CGM workshop in Sept. 2014.
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