Collaborative Research: Continuing Support for the Basin and Range Geodetic Network (BARGEN): Active Tectonics of Diffuse Intracontinental Deformation

Smithsonian Institution Astrophysical Observatory, Cambridge MA

Investigators

Abstract

0135457 Davis This award provides two years of continued support for the NSF-funded component of the Basin and Range Geodetic Network (BARGEN). This component, known as the Northern Basin and Range network or "NBAR," includes 18 remote, continuously monitored GPS sites with ~100 km spacing, deployed in an east-west array near lat. 40 deg. N, spanning the diffusely deforming western boundary of the North American plate. Installed in 1996 and 1997, these sites benefit from drilled, braced monuments anchored in bedrock to a depth of 10m and a very dry climate. Daily position estimates in the horizontal exhibit root-mean-square scatter at the 1-2 mm level, and time series analysis and other statistical analyses of some 4.5 years of data indicate errors in horizontal velocity of less than 0.2 mm/yr at one standard deviation. Continued operation of this network is urgent, because it represents an important prototype experiment for NSF's Plate Boundary Observatory (PBO) initiative, which proposes the deployment of some 900 new sites of similar design across the deforming western margin of the North American plate. The NBAR sites are scheduled to be upgraded with new instruments as early as 2004 provided PBO is funded (now under consideration as part of NSF's FY 2003 budget). The NBAR sites will form the nucleus of PBO's 100-site "backbone" network and of proposed site clusters in the northern Basin and Range. Continuity of geodetic time series up to and through PBO implementation will provide the strongest possible basis for predicting its ultimate capability, and for assessing the merits of proposed strategies for site locations. An additional two years of data from the NBAR sites will bear significantly on three fundamental - and still controversial - questions: 1) the degree to which GPS time series are contaminated by low-frequency noise; 2) whether errors in vertical velocities will be low enough to provide geophysically meaningful signal; and 3) whether to expect agreement between geodetically determined velocities and geologically determined deformation rates. Additional data will also provide the clearest possible understanding of the capabilities and limitations of continuous GPS prior to PBO deployment. ***