HR: 0830h
AN: T71E-1201
TI: Present-Day Kinematics of Crustal Deformation of the Walker Lane and Central Nevada, Derived From GPS Data
AU: * Nyst, M C
EM: nyst@geo.uu.nl
AF: USGS, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Hammond, W C
EM: bhammond@usgs.gov
AF: USGS, 345 Middlefield Road, Menlo Park, CA 94025 United States
AB: The Walker Lane (WL) is a zone of tectonic deformation located between the western edge of the Basin and Range province (BR) in Nevada and the Sierra Nevada in California. It extends from ~36$^o$ in California to ~41$^o$ latitude in western Nevada and eastern California. The WL is of great interest for the study of intra-plate deformation because it accommodates the transfer of NW directed motion of the Sierra Nevada block to roughly E-W extension in the eastern BR. In addition, by connecting the Eastern California Shear Zone (ECSZ) with more northern zones of dextral shear such as the Central Nevada Seismic Zone (CNSZ) the WL plays an important role in the accommodation of motion between the Pacific and North America plates. Previous studies of the present-day crustal deformation in this area focused on sub-regions of the WL. We study the whole WL and utilize a relatively dense GPS velocity set (of 121 stations with data from 1992 to 2002) to model crustal deformation. The GPS data set consists of the western Nevada data of Svarc et al. ({\it JGR}, {\bf 2002}), the BR data of Thatcher et al. ({\it Science}, {\bf 1999}) and the ECSZ data of Gan et al. ({\it JGR}, {\bf 2000}). Principal strain rates derived from data subsets agree with those of previous studies: In the northern WL WNW-ESE extension averages ~24 nstrain/yr and NNE-SSW contraction averages ~9 nstrain/yr. Since the average fault trend is NNW, the resulting strain rates may be indicative for dextral transtensional slip. In the central WL WNW-ESE extension (~27 nstrain/yr) and NNE-SSW contraction (~11 nstrain/yr) together with the predominantly ENE trending faults suggest sinistral transtensional slip. In the southern WL ENE-WSW extension (~25 nstrain/yr), NNW-SSE contraction (~30 nstrain/yr) and NNW trending faults correspond to dextral slip. To determine the spatial variation of the crustal deformation field we solve for a self-consistent continuous velocity gradient field from which both strain and rotation rate fields are derived. In general, the strain rate field shows a gradual change across the WL with orientations in the central WL similar to those in the CNSZ. The rotation rate field is clockwise everywhere and is especially strong in the central and southern WL.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1243 Space geodetic surveys
DE: 8107 Continental neotectonics
DE: 9350 North America
SC: Tectonophysics [T]
MN: 2002 Fall Meeting