HR: 0800h
AN: G51C-0851    [Abstracts]
TI: Evaluating Subsidence in the Central Valley, CA, using InSAR
AU: * Brandt, J T
EM: jbrandt@usgs.gov
AF: U. S. Geological Survey, 3020 State Univ. Drive East Modoc Hall Ste. 4004, Sacramento, CA 95819 United States
AU: Bawden, G W
EM: gbawden@usgs.gov
AF: U. S. Geological Survey, 3020 State Univ. Drive East Modoc Hall Ste. 4004, Sacramento, CA 95819 United States
AU: Sneed, M
EM: micsneed@usgs.gov
AF: U. S. Geological Survey, 3020 State Univ. Drive East Modoc Hall Ste. 4004, Sacramento, CA 95819 United States
AB: Satellite Interferometric Synthetic Aperture Radar (InSAR) was used to identify and characterize ground-water-induced subsidence throughout the Central Valley of California where studies show that more than 9 meters of subsidence occurred between 1925 and 1977. Subsidence measured using InSAR imagery coincides in magnitude and extent with subsidence measured during land-based geodetic surveys. Four targets in the Central Valley were chosen for this study: Highways 152 and 198 in the San Joaquin Valley; Pixley in the Wasco-Tulare area 60 km north of Bakersfield; and Davis, 15 km west of Sacramento. Precise leveling and Global Positioning System (GPS) measurements in the San Joaquin Valley (completed by the California Spatial Reference Center's San Joaquin Valley Height Modernization Project) along Highways 152 and 198 show that 1 and 2 m, respectively, of subsidence occurred from 1988 to 2003. InSAR imagery from three independent satellite tracks show a greater than 60-km-wide feature across Highway 152 and a greater than 20-km-wide deformation feature across highway 198. InSAR detects a 15- x 15-km feature just south of Pixley subsiding at a rate of about 2 cm/year between 1992 and 1995. Two overlapping satellite tracks of interferograms for this area identify a small 1.5-km-wide subsidence feature located in the southwest part of the larger-scale subsidence bowl. The maximum subsidence rate of this small-scale localized feature is approximately 35 mm/year. The Bay Area Regional Deformation (BARD) GPS site UCD1 in Davis has had an average subsidence rate of 5.7 mm/year since the site was installed in 1997. Interferograms suggest a complex seasonal deformation feature that correlates, in part, with the GPS time series.
DE: 1211 Non-tectonic deformation
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1829 Groundwater hydrology
SC: Geodesy [G]
MN: Fall Meeting 2005