Strain accumulation and rotation in western Nevada, 1993–2000

Abstract

The positions of 44 GPS monuments in an array extending from the Sierra Nevada at the latitude of Reno to near Austin, Nevada, have been measured several times in the 1993–2000 interval. The western half of the array spans the Walker Lane belt, whereas the eastern half spans the central Nevada seismic zone (CNSZ). The principal strain rates in the Walker Lane belt are 29.6 ± 5.3 nstrain yr −1 N88.4°E ± 5.4° and −12.8 ± 6.0 nanostrain yr −1 N01.6°W ± 5.4°, extension reckoned positive, and the clockwise (as seen from above the Earth) rotation rate about a vertical axis is 13.6 ± 4.0 nrad yr −1 . The quoted uncertainties are standard deviations. The motion in the Walker Lane belt can then be represented by a zone striking N35°W subject to 16.8 ± 4.9 nstrain yr −1 extension perpendicular to it and 19.5 ± 4.0 nstrain yr −1 right‐lateral, simple shear across it. The N35°W strike of the zone is the same as the direction of the local tangent to the small circle drawn about the Pacific‐North America pole of rotation. The principal strain rates for the CNSZ are 46.2 ± 11.0 nstrain yr −1 N49.9°W ± 6.0° and −13.6 ± 6.1 nstrain yr −1 N40.1°E ± 6.0°, and the clockwise rotation rate about a vertical axis is 20.3 ± 6.3 nrad yr −1 . The motion across the CNSZ can then be represented by a zone striking N12°E subject to 32.6 ± 11.0 nstrain yr −1 extension perpendicular to it and 25.1 ± 6.3 nstrain yr −1 right‐lateral, simple shear across it. The N12°E strike of the zone is similar to the strikes of the faults (Rainbow Mountain, Fairview Peak, and Dixie Valley) within it.