BARGEN continuous GPS data across the eastern Basin and Range province, and implications for fault system dynamics

Abstract

We collected data from a transect of continuous Global Positioning System (GPS) sites across the eastern Basin and Range province at latitude 39°N from 1997–2000. Intersite velocities define a region ~350 km wide of broadly distributed strain accumulation at ~10 nstr yr^(−1). On the western margin of the region, site EGAN, ~10 km north of Ely, Nevada, moved at a rate of 3.9 ± 0.2 mm yr^(−1) to the west relative to site CAST, which is on the Colorado Plateau. Velocities of most sites to the west of Ely moved at an average rate of ~3 mm yr^(−1) relative to CAST, defining an area across central Nevada that does not appear to be extending significantly. The late Quaternary geological velocity field, derived using seismic reflection and neotectonic data, indicates a maximum velocity of EGAN with respect to the Colorado Plateau of ~4 mm yr^(−1), also distributed relatively evenly across the region. The geodetic and late Quaternary geological velocity fields, therefore, are consistent, but strain release on the Sevier Desert detachment and the Wasatch fault appears to have been anomalously high in the Holocene. Previous models suggesting horizontal displacement rates in the eastern Basin and Range near 3 mm yr^(−1), which focused mainly along the Wasatch zone and Intermountain seismic belt, may overestimate the Holocene Wasatch rate by at least 50 per cent and the Quaternary rate by nearly an order of magnitude, while ignoring potentially major seismogenic faults further to the west.

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