HR: 1400h
AN: G43B-06    [Abstracts]
TI: Contemporary Deformation within the Snake River Plain and Northern Basin and Range Province, USA
AU: * Payne, S J
EM: Suzette.Payne@inl.gov
AF: Idaho National Laboratory, P.O. Box 1625, MS 2025, Idaho Falls, ID 83415, United States
AU: McCaffrey, R
EM: mccafr@rpi.edu
AF: Rensselaer Polytechnic Institute, Department of Earth and Environmental Sciences, Troy, NY 12180, United States
AU: King, R W
EM: rwk@chandler.mit.edu
AF: Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA 02139, United States
AB: GPS velocities, earthquakes, faults, and volcanic features are used to evaluate contemporary deformation within the Snake River Plain (SRP) and surrounding northern Basin and Range Province. The SRP is a prominent low- relief physiographic feature that extends from eastern Oregon through southern Idaho and into northwestern Wyoming, USA. The Eastern Snake River Plain (ESRP) is a 400-km long, NE-trending volcanic province that is characterized by bimodal volcanism, which represents the track of the Yellowstone Hotspot currently located in Wyoming. The Western Snake River Plain (WSRP) is a 300-km long, NW-trending graben that extends into eastern Oregon. The WSRP is an extensional basin that formed adjacent to an earlier position of the Yellowstone Hotspot in southern Idaho. Previous geodetic investigations suggest the ESRP and, perhaps the WSRP, have GPS velocities indicative of rigid block motion of the SRP along its physiographic boundaries. GPS data compiled for this study are used to test this hypothesis. Several institutions including the National Geodetic Survey, Idaho National Laboratory, Rensselaer Polytechnic Institute, and University of Utah observed GPS stations from 1994 to 2006 within the SRP and surrounding region. Horizontal velocities show generally consistent N110°W orientations with an average rate of 1.5 ± 0.3 mm/yr (for 11 stations) along most of the ESRP and adjacent northwest Basin and Range, although some Basin and Range velocities are less and may be influenced by post viscoelastic relaxation following the 1983 Mw 6.9 normal-faulting Borah Peak, Idaho earthquake. GPS velocities with an average rate of 1.9 ± 0.3 mm/yr (for 5 stations) change orientation to N95°W at a distance of 190 km from the Yellowstone Hotspot within the southern region of the ESRP and adjacent Basin and Range. Within the WSRP, GPS velocities have an average rate of 2.0 ± 0.5 mm/yr (for 7 stations) and change orientation to N40°W. These GPS velocities are more consistent with those in eastern Oregon, a region that is rotating clockwise relative to North America. To assess possible rotations and strain rates, we invert GPS horizontal velocities, geologic fault slip rates, earthquake-derived fault slip vector azimuths, and volcanic dike extension rates. We interpret GPS velocities to describe the relative motions of coherent regions of consistent strain within the SRP and surrounding Basin and Range Province.
DE: 1209 Tectonic deformation (6924)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
SC: Geodesy [G]
MN: 2007 Joint Assembly