Magnetotelluric data release across the Hubbell Springs fault area, Middle Rio Grande Basin, New Mexico

The population in the Albuquerque-Santa Fe region of New Mexico is rapidly growing. The Santa Fe Group aquifer in the Middle Rio Grande Basin is the main source of municipal water for the greater Albuquerque metropolitan area. The capacity of this aquifer is more limited than previously thought (Thorn et al.,1993). The Middle Rio Grande Basin, as defined hydrologically and used here, is the area within the Rio Grande Valley extending from Cochiti Dam downstream to the community of San Acacia. Because approximately 600,000 people (40 percent of the population of New Mexico) live in the study area (Bartolino, 1999), water shortfalls could have serious consequences. Future growth and land management in the region depends on accurate assessment and protection of the region's groundwater resources. An important issue in defining the ground water resources is a better understanding of the hydrogeology of the Santa Fe Group and the other sedimentary deposits that fill the Rio Grande rift. The U.S. Geological Survey (USGS) is currently conducting a series of studies of the Middle Rio Grande Basin in north-central New Mexico to address this issue. One objective of these studies is to improve the hydrogeologic models of the Middle Rio Grande Basin to help land managers plan for the development and use of its water resources. These studies involve a multi-disciplinary approach to better understand the critical aquifers in what is considered to be an intracontinental rift environment. Detailed geologic mapping, high-resolution airborne magnetic surveys, lithologic and geophysical logging of wells, surface-based electrical, gravity and magnetic surveys, enhanced satellite imagery, as well as hydrologic and hydrogeochemical data are being used to refine our understanding of the aquifer systems in the Middle Rio Grande Basin (Cole et al., 1999). This report presents a description of the magnetotelluric soundings that are being used to constrain gravity modeling across the Hubbell Springs fault, a fault that offsets lithologic units important to the critical aquifers. The purpose of this report is to release the magnetotelluric sounding data; no interpretation of the data is included.