HR: 0800h
AN: G21B-0500 INVITED    [Abstracts]
TI: Finding and Defining the Edges of Stable North America: Reference Frame Effects versus Real Tectonics
AU: * Kreemer, C
EM: kreemer@unr.edu
AF: Nevada Bureau of Mines and Geology, University of Nevada, Reno 1664 N. Virginia Street, Reno, NV 89557-0178, United States
AU: Blewitt, G
EM: gblewitt@unr.edu
AF: Nevada Bureau of Mines and Geology, University of Nevada, Reno 1664 N. Virginia Street, Reno, NV 89557-0178, United States
AB: The main significance of the new Stable North American Reference Frame (SNARF) is to provide a unique reference frame in which to analyze and interpret GPS velocities in the Pacific-North American plate boundary zone. SNARF is determined while taking into account the effect of glacial isostatic rebound, but is not implicitly constrained to yield crustal velocities across the western margin of the stable continent that are consistent with other geophysical and tectonic indicators. For instance, one would expect SNARF-fixed velocities east of the Rocky Mountains and Rio Grande Rift to be insignificant from zero, but the question is still open whether they are. At the same time, the location of the edge of the stable continent in the northern Rockies and in Alaska is still unknown and SNARF-fixed velocities may be instrumental in defining this edge. However, our ability to find and define the edge of the stable continent relies generally on the adequateness of SNARF and may depend particularly on the way we realize the SNARF-fixed velocity field. To address these issues we derive and use a GPS velocity field from a ~600 station network across the North American continent. Data come from a variety of continuous GPS networks, including PBO and CORS, but also include data from semi-continuously observed sites observed by us in the Great Basin. The daily positions are determined with the GIPSY-OASIS II software, have fixed ambiguities, and are adjusted for regional common- mode effects. We show crustal velocity fields in a variety of reference frames, including various realizations of SNARF, and discuss them with respect to the regional tectonics. These exercises are important both to assess the validity and applicability of SNARF, and also to address, for example, whether the Rio Grande Rift is still active, or if any part of Alaska can be considered part of stable North America.
UR: http://geodesy.unr.edu
DE: 1209 Tectonic deformation (6924)
DE: 1229 Reference systems
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 8150 Plate boundary: general (3040)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2007 Fall Meeting