HR: 14:40h
AN: T32D-05    [PDF]
TI: SAR Interferometry for Measuring Recent Deformation of the Eastern Snake River Plain
AU: * Chadwick, J
EM: chadjohn@isu.edu
AF: Idaho State University, Dept. of Geosciences, Pocatello, ID 83209 United States
AU: Rodgers, D
EM: rodgdavi@isu.edu
AF: Idaho State University, Dept. of Geosciences, Pocatello, ID 83209 United States
AU: Payne, S
EM: MSJ1@inel.gov
AF: Idaho National Engineering and Environmental Laboratory, Geosciences Research Dept., Idaho Falls, ID 83415 United States
AB: The Eastern Snake River Plain (ESRP) is a NE-trending volcanic basin that defines the track of the Yellowstone hotspot across southern Idaho. Previous studies of the ESRP interpreted up to 6 km of upper crustal subsidence and 15-25 % extension since 10-15 Ma. Leveling studies conducted between 1906 and 1983 and more recent GPS studies indicate that at least some ESRP regions continue to actively extend and/or subside. To document the regional pattern of active deformation, we have employed interferometric synthetic aperture radar (InSAR) techniques. Snow- and rain-free ERS-1 and ERS-2 SAR images from 1992-2003 with less than 400 m baselines were acquired for areas with large, young basaltic lava flows with flat surfaces, sparse vegetation and little soil cover, such as the Craters of the Moon, Wapi, and Hell's Half-Acre lava fields. These areas are ideal for preserving surface characteristics and maintaining SAR phase coherence between images for 4-10 years, time spans that are required to detect the slow rates of topographic change on the ESRP. Results from the Wapi region indicate that differential subsidence and/or extension from 1993-1997 was symmetrically disposed about the axis of the Great Rift, with greater Line of Sight (LOS) topographic change on the margins and less along the rift. Results from the Craters of the Moon region indicate variable amounts of upper crustal subsidence and extension from 1993-1997, although the absolute amount requires further calibration by GPS analysis. Up to 2 mm/yr of differential LOS change is evident in the region over this period, with a domain of less LOS change across the axis of the Great Rift and a domain of greater LOS change to the west. The line that separates domains is relatively sharp, oriented north-northwest, and if extrapolated northward is on strike with the surface trace of a west-dipping Basin-Range normal fault. One interpretation of this pattern is that Basin-Range half-graben fault blocks underlie the ESRP. Alternatively, the observed pattern of differential uplift may be part of a larger, symmetrical pattern characterized by greater subsidence on the flanks of the Great Rift than along its axis. Further testing of these hypotheses will occur through field study of the Basin-Range fault kinematics and a GPS campaign scheduled for the Fall of 2003 to previously surveyed sites in the study area.
DE: 8010 Fractures and faults
DE: 8040 Remote sensing
DE: 8105 Continental margins and sedimentary basins
DE: 8109 Continental tectonics--extensional (0905)
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting