HR: 09:45h
AN: G31D-07    [Abstracts]
TI: Crustal Deformation across the Sierra Nevada-Northern Walker Lane, Basin and Range Transition, Western United States Measured with GPS, 2000-2004
AU: * Hammond, W C
EM: whammond@unr.edu
AF: Nevada Bureau of Mines and Geology, University of Nevada MS 178, Reno, NV 89557 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
AU: Blewitt, G
EM: gblewitt@unr.edu
AF: Nevada Bureau of Mines and Geology, University of Nevada MS 178, Reno, NV 89557 United States
AB: In the northern Walker Lane (WL) of northwest Nevada and northeast California, approximately 20-25% of the contemporary Pacific/North America relative plate motion is accommodated east of the Sierra Nevada in a focused zone of dextral shear and extension. Previous measurements with the Global Positioning System (GPS) have identified a partitioning of shear and extension and a widening of the zone of active deformation north of 39? north latitude. This deformation pattern may indicate that northwest-directed extension in the Basin and Range east of the WL becomes more active northward, making up for a northward decrease in northwest-directed dextral slip on the WL strike slip faults. Alternatively (or additionally), it may be an effect of postseismic relaxation following the 20th century earthquakes in the Central Nevada Seismic Belt (CNSB), east of the WL. We present velocities and strain rate tensors obtained from newly collected GPS data along networks that extend from the Central Great Valley of California, across the Sierra Nevada, Walker Lane and into the central Basin and Range province. Campaign surveys in September 2000 and September 2004 occupied 56 sites that have greater spatial density ($<$20 km), and lie outside the footprint of the planned deployment of the Plate Boundary Observatory Extension/Backbone continuous GPS cluster. These networks fill gaps in previous GPS coverage, and between the sparsely (near 100 km) spaced continuously recording Basin and Range Geodetic Network (BARGEN), whose data we include in our GIPSY/OASIS II processing. Additionally, our solution will include GPS data from 40+ stations of a new network of semi-continuous sites: the Nevada Mobile Array of GPS for Nevada Transtension (MAGNET), which commenced operation the end of January 2004 and currently has $<$1 year of data, but provides a complementary spatial distribution of sites and will, in future, greatly enhance constraint on WLB surface deformation. We will use the combined solution to provide new constraints on postseismic relaxation on the CNSB and on plate boundary kinematics in the northern WL.
DE: 8110 Continental tectonics--general (0905)
DE: 8122 Dynamics, gravity and tectonics
DE: 8159 Rheology--crust and lithosphere
DE: 1208 Crustal movements--intraplate (8110)
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting