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HR: 0800h
AN: G21A-0658
TI: GPS Velocity and Strain Rate Fields in the Great Basin and California
AU: * Blewitt, G
EM: gblewitt@unr.edu
AF: Nevada Bureau of Mines and Geology, and Seismological Laboratory, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, United States
AU: Kreemer, C
EM: kreemer@unr.edu
AF: Nevada Bureau of Mines and Geology, and Seismological Laboratory, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, United States
AU: Hammond, W C
EM: whammond@unr.edu
AF: Nevada Bureau of Mines and Geology, and Seismological Laboratory, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, United States
AU: Plag, H
EM: hpplag@unr.edu
AF: Nevada Bureau of Mines and Geology, and Seismological Laboratory, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, United States
AB: New data from EarthScope's Plate Boundary Observatory (PBO) allow for an improved spatial resolution of crustal motion in the Pacific-North America plate boundary zone. In addition to PBO and other GPS networks (BARGEN, BARD, SCIGN, EBRY, CORS) we further increased densification between the northern Walker Lane and the Garlock fault by establishing the 300+ station NEARNET network. The first NEARNET sites were established in 2004, with the core part of the network (known as MAGNET) being measured semi- continuously. Sites on the fringes of the network are measured every 1-2 years, with each occupation being at least 3 weeks. We routinely analyze NEARNET data together with those from all publicly available continuous sites in the western United States (and most other sites in the rest of the world) with the GIPSY precise point positioning software, and routinely produce solutions that have phase ambiguities resolved using Ambizap. Position time-series are relative to stable North America and have common-mode errors removed on both the continental scale as well as on the scale of the Great Basin, western United States. We present velocities for all sites with time-series longer than 2 years, together with velocity uncertainties that account for the presence of colored-noise. We aim to remove all significant co- and post-seismic deformation from recent earthquakes that significantly affect the estimate of the secular motion. The dense GPS velocity field in California and the western Great Basin provides the critical input to refine the crustal deformation field, and hence improve understanding of western U.S. lithospheric dynamics and seismic hazard. Here we present a high-resolution strain rate map for all of California and the Great Basin using a spline interpolation and least-squares fit to the GPS velocities. For this model we also include published GPS velocities obtained from campaign-style measurements. The resolution of our model allows, for the first time, to identify strain localization across individual strands of fast-slipping faults. We also include geologically estimated fault slip rate information to better relate strain to fault structures which is especially important to relate geodetic strain to faults in the eastern part of the plate boundary zone. To illustrate how the strain rate map can provide a base map of interseismic strain accumulation for InSAR studies, we present an InSAR equivalent fringe-map of expected line-of-sight rates from our model. An additional analysis of the statistics of seismic versus tectonic moment release based on our strain rate model is presented elsewhere (Torres et al., Statistics and Correlations of Seismic and Tectonic Moment Rate in California and the Great Basin, session NG04).
UR: http://geodesy.unr.edu/networks/
DE: 1209 Tectonic deformation (6924)
DE: 1243 Space geodetic surveys
DE: 8110 Continental tectonics: general (0905)
DE: 8150 Plate boundary: general (3040)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2008 Fall Meeting