During the Summer of Applied Geophysical Experience (SAGE) in 2002 a magnetotelluric profile was set up on Cochiti Pueblo reservation land in the Santo Domingo Basin, which lies in the north-central portion of the Rio Grande Rift, New Mexico. The data were used to generate 2-D electrical resistivity models of the subsurface. The purpose of the modeling and analysis was to compare and further constrain the extent of the La Bajada Fault, an unnamed fault, a Tertiary monzonite intrusive (groundwater barrier), and groundwater salinity described by Quesada (2004). Regularized inverse modeling was accomplished using Winlink software, which is based on a nonlinear conjugate gradients algorithm (Rodi and Mackie, 2001). The modeling successfully imaged the unnamed fault, the La Bajada Fault, and possibly part of the monzonite intrusive. The 1_11odels correlated well with a USGS reduced-to-pole magnetic map, gravity maps of the Cochiti Pueblo, and proprietary industry seismic reflection data. Modeling results from the 2002 MT data strongly correlated with modeling and analysis by Quesada (2004). In conclusion, the MT method provided valuable constraints on groundwater resources, groundwater quality, and geologic structure.
