HR: 0830h
AN: G71A-0952
TI: Crustal Deformation Across the Basin and Range Province, Western United States, Measured with the Global Positioning System, 1992-2002
AU: * Hammond, W C
EM: bhammond@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS/977, Menlo Park, CA 94025 United States
AU: Thatcher, W
EM: thatcher@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd. MS/977, Menlo Park, CA 94025 United States
AB: The Basin and Range province of the western United States lies east of the Sierra Nevada mountains and accommodates roughly 25% of the motion between the North American and Pacific Plates in this region. It is experiencing both active extension and dextral shear, whose orientation is consistent with relative plate motion, suggesting that the province is an important part of the overall plate boundary system. We present results from recent measurement of Basin and Range crustal motion using the Global Positioning System (GPS). As of September 2002, ten years of deformation will have been observed with GPS measurements in 1992,1996, 1998 and 2002. The 800 km long east-to-west line of campaign-style geodetic benchmarks extends from east of the Wasatch fault zone in Utah to west of the Genoa fault zone and Lake Tahoe in California's Northern Sierra Nevada mountains, primarily along Interstate Highway 50. In all there are velocities at 91 GPS sites, nearly double the number previously presented (Thatcher et al. [1999]), all of which will be measured in September 2002. Incorporating this new data is expected to reduce the uncertainty in earlier measurements that show the motion of the Sierra Nevada block with respect to non-deforming North America to be accommodated by right lateral shear and extensional deformation in Nevada and Utah. Velocity variation of about 9 mm/yr is concentrated in the western one-third of the network, with a lesser amount (roughly 3 mm/yr) localized to the easternmost edge of the network, in the vicinity of the Wasatch fault zone. Recent densification of the GPS network across these two zones will also improve the spatial resolution of the deformation in these regions. The greatest rate of present-day deformation occurs near the ruptures of the Fairview Peak and Rainbow Mountain earthquakes in the Central Nevada Seismic Zone, extending west past the Genoa fault into the Sierra Nevada. This strain rate pattern is correlated with the concentration of historic faulting and seismicity in the western half of Nevada and eastern California, but is less well correlated with the relatively broad distribution of faults with Holocene and late Quaternary age. To process the data we use the GIPSY/OASIS II and Quasi-Observation Combination Analysis (Dong et al. [1998]) software packages and incorporate data from continuously recording GPS stations in California and Nevada.
DE: 1208 Crustal movements--intraplate (8110)
DE: 8122 Dynamics, gravity and tectonics
DE: 8150 Plate boundary--general (3040)
DE: 9350 North America
SC: Geodesy [G]
MN: 2002 Fall Meeting