Abstract Title: Temporal variations of geodetic velocities in the Basin and 
Range

Abstract Author(s): Davis, James (Harvard-Smithsonian Center for 
Astrophysics)-Wernicke, Brian (California Institute of Technology)-Bennett, 
Richard (Harvard-Smithsonian Center for Astrophysics)  

Abstract: We have used time series of estimated horizontal site positions from 
GPS to address the issue of recent temporal variations of crustal velocity in 
the Basin and Range. We have begun by estimating horizontal acceleration of 
site position in the northern BARGEN network, where we have the longest time 
series (starting in mid-1996). The estimates yield accelerations of ~0.4 
mm/yr^2 in the western part of the network, much larger than those in the 
eastern network. The directions are fairly coherent except for several sites 
within the Nevada Seismic Zone, which may be influenced by several nearby large 
(M>6.5) earthquakes (Pleasant Valley, 1915; Cedar Mountain, 1932; Dixie Valley, 
1954; and Fairview Peak, 1954). Based on the velocity field for the period 
1996.5-2000, Wernicke et al. [2000] had reported that these earthquakes may be 
responsible for ongoing transient deformation. In the eastern part of the 
network, the accelerations are generally less than 0.1 mm/yr^2, except for 
sites COON and EGAN. COON suffers significantly from the effect of crustal 
loading associated with Great Salt Lake water-level variation. The acceleration 
at EGAN is similar to those of the western network, and is difficult to explain 
in terms of either hydrological or post-seismic rebound effects. We present the 
acceleration field, and discuss its possible significance in terms of the 
geophysics and geodesy of the Basin and Range. We also discuss the issues 
associated with assessing the statistical significance of this new geodetic 
observable in view of known sources of error.