HR: 1340h
AN: T33C-1394    [Abstracts]
TI: Results of the 2004 GPS Study of Extension Rates in the Eastern Snake River Plain, Idaho
AU: * Chadwick, J
EM: chadjohn@isu.edu
AF: Dept. of Geosciences, Idaho State University, Pocatello, ID 83209 United States
AU: Payne, S
EM: MSJ1@inel.gov
AF: Geosciences Research Dept., Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID 83415 United States
AB: Previous investigators suggest the eastern Snake River Plain (ESRP) is extending by dike intrusion, which enables it to keep pace with SW-NE extension that is occurring in the surrounding Basin and Range Province. Northwest-trending, linear eruptive fissures and aligned volcanic vents within ESRP volcanic rift zones provide observational evidence for dike intrusion in the ESRP as recent as 2000 yrs ago. To assess the amount of extension occurring in the ESRP, a campaign GPS survey was conducted in April of 2004 by Idaho State University and the Idaho National Engineering and Environmental Laboratory. Twenty benchmarks located within the ESRP and adjacent northwest Basin and Range (Lost River and Beaverhead Ranges, Idaho) were each occupied for 48 to 96 hours using Trimble 4000 dual frequency GPS receivers supplied by UNAVCO. The University of Utah occupied these same benchmarks in 1995 and 2000, resulting in three occupations over nine years. Preliminary results suggest that benchmarks on the ESRP consistently moved southwest relative to a fixed North American reference, and rates systematically increased from northeast (near Rexburg, Idaho) to southwest (near Twin Falls, Idaho) for the nine year time period. Benchmarks in the adjacent northwest Basin and Range also moved southwest at comparable rates, and an increase in displacement rate from NE to SW is also apparent, although it is not as systematic. The preliminary results suggest the strain measured over nine years is similar in the ESRP and adjacent northwest Basin and Range, and thus, no differential movement is indicated. To supplement the GPS results, an interferometric synthetic aperture radar (InSAR) study of the ESRP is also underway using European Resource Satellite (ERS-1 and ERS-2) images. The anticipated results of the InSAR study will provide more spatially detailed and coherent information about differential movements within the ESRP, beyond what is shown by the GPS study.
DE: 8010 Fractures and faults
DE: 8109 Continental tectonics--extensional (0905)
DE: 1208 Crustal movements--intraplate (8110)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting