HR: 0830h
AN: G31B-0703    [PDF]
TI: Testing intraplate deformation in the North American plate interior from a combined geodetic solution: implication for strain accumulation on potentially seismogenic faults in the central and eastern U.S.
AU: * Song, Y
EM: song7@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47906-2051 United States
AU: Calais, E
EM: ecalais@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences, 550 Stadium Mall Drive, West Lafayette, IN 47906-2051 United States
AU: Demets, C
EM: chuck@geology.wisc.edu
AF: University of Wisconsin, 1215 W Dayton St., Madison, WI 53706 United States
AU: Nocquet, J
EM: Jean-Mathieu.Nocquet@earth.ox.ac.uk
AF: Oxford University, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AB: Large earthquakes within stable plate interiors, such as the 1811-1812 New Madrid events in the Mississippi valley, are direct evidence that significant levels of strain can accumulate along geologic structures far from plate boundary faults. However, direct geodetic measurement of present-day horizontal strain in the Central and Eastern US is challenging because of the low strain rate relative to the underlying geodetic noise and difficulties in accurately estimating geodetic site velocity uncertainties. In an attempt to rigorously assess crustal strain rates in the central and eastern United States, we combined independent geodetic solutions based on ~300 continuous geodetic stations covering the stable interior of the North American plate. The combination includes daily GPS solutions computed at Univ. Wisconsin with GIPSY-OASIS and at Purdue University with GAMIT that range from 1996 to 2003, as well as IGS weekly combined solutions, and the full ITRF2000 solution, which also serves as reference frame. We emphasize realistic assessments of velocity uncertainties through a variety of techniques, including use of the full covariance matrix of the geodetic solutions in the combination and assorted statistical tests meant to detect regionally coherent departures from plate rigidity. We present our most recent horizontal velocity field and vertical rates for the central and eastern US, including a comparison of the 3D velocity fields defined independently from the GIPSY and GAMIT analyses. Preliminary conclusions regarding upper bounds on deformation in this region will be presented, as will residual site velocities as a function of the type of antenna mounting structure.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1229 Reference systems
DE: 7205 Continental crust (1242)
DE: 7223 Seismic hazard assessment and prediction
DE: 8109 Continental tectonics--extensional (0905)
SC: Geodesy [G]
MN: 2003 Fall Meeting