Cooperative Institute for Research in Environmental Sciences

Reducing the Uncertainty in the Estimation of Deformation across the Rio Grande Rift Region

James Choe1, R. Steven Nerem1,3, Anne Sheehan2,3, Henry Berglund4, Mark H. Murray5

1Department of Aerospace Engineering Sciences, University of Colorado, Boulder CO 80309 2Department of Geological Sciences, University of Colorado, Boulder CO 80309 3Cooperative Institute for Research in Environmental Sciences, Boulder CO 80309 4UNAVCO, Boulder, Colorado 80301 5Department of Earth & Environmental Science, New Mexico Tech, Socorro, NM 87801

We analyze over 5 years of continuous GPS measurements from 25 GPS sites across the Rio Grande Rift (RGR) region in New Mexico and Colorado. Plate Boundary Observatory (PBO) GPS sites in adjoining eastern Colorado Plateau and western Great Plains are also included in the analysis. Surface velocities for each GPS sites are computed by GIPSY/OASIS in a North America fixed reference frame and are used to derive strain-rate deformation in the RGR region. The time series from the first 5 years are also examined to assess RGR site stability. An attempt is made to estimate the surface loading correction due to hydrology from Gravity Recovery and Climate Experiment (GRACE) measurements over the same time period. This correction is applied on the vertical time series to better model annual displacement on the surface velocity estimation and to reduce the uncertainty in the strain-rate estimation.