This research involves the seismological investigation of the crust and mantle beneath a transect extending from the Great Plains of western Texas through the Rio Grande rift and well into the Colorado Plateau. By means of PASSCAL portable seismographs, scientists from four institutes (University of Texas at Austin, New Mexico State University, New Mexico Institute of Mining and Technology, and the Los Alamos National Laboratory) will occupy an 1100-km line for 10-12 months recording naturally occurring earthquakes. Seismic body-wave (P and S) and surface-wave data will be collected to enable the construction of detailed two-dimensional maps of P and S velocities beneath this portion of the southwestern United States. This mapping will be used to address questions such as the cause of the uplift of the Colorado Plateau, the depth of mantle processes that control surface tectonics, the connection between mantle and crustal strain beneath the Rio Grande Rift, and the location of the subducted Farallon plate. Integration of surface geological information with the deep structure images will result in a more complete regional tectonic model and a better understanding of the causes of the dramatic tectonic events that have occurred during the last 40 million years in this region.
