HR: 11:20h
AN: T22A-05    [Abstracts]
TI: Evidence for Right-lateral Shear Along the Northwest Margin of the Eastern Snake River Plain, Idaho
AU: * Payne, S J
EM: Suzette.Payne@inl.gov
AF: Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415, United States
AU: McCaffrey, R
EM: R.McCaffrey@gns.cri.nz
AF: GNS Science, PO Box 30368, Lower Hutt, 5040, New Zealand
AU: King, R W
EM: rwk@chandler.mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
AB: Previous investigators have proposed that extension within the eastern Snake River Plain (ESRP) is accommodated by intrusion of dikes at a rate similar to the rate of extension in the surrounding Basin and Range. This hypothesis is primarily based on the lack of strike-slip offset along the northwest physiographic boundary of the ESRP, the lack of seismicity within the ESRP relative to the surrounding active Basin and Range, and the presence of NW-trending volcanic rift zones within the ESRP. The ESRP is a 400-km long region within the track of the Yellowstone Hotspot that extends from southern Idaho northeast into northwestern Wyoming. GPS data compiled for this study are used to test this hypothesis. Several institutions including the Idaho National Laboratory, National Geodetic Survey, Rensselaer Polytechnic Institute, and University of Utah observed GPS stations from 1994 to 2007 within the ESRP and surrounding region. The GPS velocities show the average orientation of horizontal GPS velocities in the adjacent northwest Basin and Range region is similar to the average orientation for the ESRP (N113°W vs N91°W, respectively), but the average magnitude of horizontal GPS velocities in the Basin and Range (1.4 ± 0.3 mm/yr) is less than that for the ESRP (2.2 ± 0.3 mm/yr). Additionally, the adjacent northwest Basin and Range extends at about 9 x 10^-9 /yr with most of the deformation localized along three NW-trending normal faults (Lost River, Lemhi, and Beaverhead). In contrast, the ESRP extends at a rate that is an order of magnitude lower than the adjacent northwest Basin and Range and we see little indication of extension along the Great Rift or other volcanic rift zones over the 400 km length. The GPS differential motion along the region of the ESRP adjacent to the northwest Basin and Range indicates a NE-trending zone of right-lateral shear. Preliminary inversions of GPS velocities, earthquakes, faults, and volcanic features indicate this zone of right-lateral shear is located 10-20 km from the physiographic boundary between the ESRP and adjacent Basin and Range.
DE: 8107 Continental neotectonics (8002)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8145 Physics of magma and magma bodies
DE: 9350 North America
SC: Tectonophysics [T]
MN: 2007 Fall Meeting