CONSTRAINTS ON PRESENT-DAY BASIN AND RANGE DEFORMATION FROM SPACE GEODESY

We use new space geodetic data from very long baseline interferometry and satellite laser ranging combined with other geodetic and geologic data to study contemporary deformation in the Basin and Range province of the western United States. Northwest motion of the central Sierra Nevada block relative to stable North America, a measure of integrated Basin and Range deformation, is 12.1+/-1.2 mm/yr oriented N38 degrees W+/-5 degrees (one standard error), in agreement with previous geological estimates within uncertainties. This velocity reflects both east-west extension concentrated in the eastern Basin and Range and north-northwest directed right lateral shear concentrated in the western Basin and Range. Fly, Nevada is moving west at 4.9+/-1.3 mm/yr relative to stable North America, consistent with dip-slip motion on the north striking Wasatch fault and other north striking normal faults. Comparison with ground-based geodetic data suggests that most of this motion is accommodated within similar to 50 lan of the Wasatch fault zone. Paleoseismic data for the Wasatch fault zone and slip rates based on seismic energy release in the region both suggest much lower slip rates. The discrepancy may be explained by some combination of additional deformation away from the Wasatch fault itself, aseismic slip, or a seismic rate that is anomalously low with respect to longer time averages. Deformation in the western Basin and Range province is also largely confined to a relatively narrow boundary zone and in our study area is partitioned into the eastern California shear zone, accommodating 10.7+/-1.6 mm/yr of north-northwest directed right-lateral shear, and a small component (similar to 1 mm/yr) of west-southwest - east-northeast extension. A slip rate budget for major strike-slip faults in our study area based on a combination of local geodetic or late Quaternary geologic data and the regional space geodetic data suggests the following rates of right-lateral slip: Owens Valley fault zone, 3.9+/-1.1 mm/yr; Death Valley-Furnace Creek fault zone, 3.3+/-2.2 mm/yr; White Mountains fault zone in northern Owens Valley, 3.4+/-1.2 mm/yr; Fish Lake Valley fault zone, 6.2+/-2.3 mm/yr. In the last few million years the locus of right-lateral shear in the region has shifted west and become more north trending as slip on the northwest striking Death Valley-Furnace Creek fault zone has decreased and is increasingly accommodated on the north-northwest striking Owens Valley fault zone.