Wernicke, Brian and Davis, James L. and Bennett, Richard A. and Normandeau, James E. and Friedrich, Anke M. and Niemi, Nathan A. (2004) Tectonic implications of a dense continuous GPS velocity field at Yucca Mountain, Nevada. Journal of Geophysical Research B, 109 (B12). Art. No. B12404. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20101118-104543598
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A dense, continuous GPS network was established in the Yucca Mountain area in 1999 to provide the most reliable measurements possible of geodetic strain patterns across the nation's only proposed permanent repository for high-level radioactive waste. The network lies astride a boundary between the geodetically stable central Great Basin and the active western Great Basin, which at the latitude of Yucca Mountain is undergoing distributed right-lateral shear at a rate of ~60 nstrain/yr. Monitoring from 1999 to 2003 (3.75 years) yields a velocity field characterized by nearly homogenous N20°W right-lateral shear of 20 ± 2 nstrain/yr (net velocity contrast of ~1.2 mm/yr across a 60 km aperture) in the vicinity of the proposed repository site. Comparison of time series of continuous results with earlier campaign surveys indicating ~50 nstrain/yr of west-northwest extension from 1991 to 1997 suggests that the more rapid rates were in part transient motions associated with the 1992 M s 5.4 Little Skull Mountain earthquake. Postseismic motions do not appear to affect the 1999–2003 velocity field in either campaign or continuous data. The magnitude of the velocity contrast across the area, the overall linearity of the gradient, and the large area of undeforming crust to the east of Yucca Mountain are difficult to explain by elastic bending of the crust associated with the Death Valley fault zone, a major right-lateral strike-slip fault about 50 km west of the repository site. These observations, along with apparent local variations in the velocity gradient, suggest that significant right-lateral strain accumulation, with displacement rate in the 1 mm/yr range, may be associated with structures in the Yucca Mountain area. The absence of structures in the area with equivalent late Quaternary displacement rates underscores the problem of reconciling discrepancies between geologic and geodetic estimates of deformation rates.
|Additional Information:||© 2004 American Geophysical Union. Received 7 October 2003; revised 3 July 2004; accepted 8 September 2004; published 15 December 2004. This research was supported by DOE contract FC-08-98NV12081. Operation and analysis of the northern part of the BARGEN network was supported by NSF grants EAR-0135457 and EAR-0136102. Geodetic sites were constructed with technical assistance from the University NAVSTAR Consortium (UNAVCO) facility. Several of the figures were prepared using Generic Mapping Tools (GMT) version 3.4.2 [Wessel and Smith, 1998]. We are grateful to T. Herring for sharing calculations on postseismic effects of the Hector Mine earthquake in the Yucca Mountain area, and J. Price and G. Blewitt for discussions. We thank reviewers T. H. Dixon and J. C. Savage, and Associate Editor Y. Bock for constructive suggestions that substantially improved the quality of the manuscript.|
|Group:||Caltech Tectonics Observatory|
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|Official Citation:||Wernicke, B., J. L. Davis, R. A. Bennett, J. E. Normandeau, A. M. Friedrich, and N. A. Niemi (2004), Tectonic implications of a dense continuous GPS velocity field at Yucca Mountain, Nevada, J. Geophys. Res., 109, B12404, doi:10.1029/2003JB002832|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||18 Nov 2010 21:24|
|Last Modified:||26 Dec 2012 12:39|
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