This research will use the PASSCAL digital recorders and three- component broadband seismometers along with the permanent IRIS station at Albuquerque. Data will be used to perform receiver- function-method inversion for crustal and upper mantle structure along the Rio Grande Rift in New Mexico. Questions to be addressed include the nature of the mid-crustal transition and possible low-velocity layer and the structure of the upper mantle. The results would provide insights into the relationship between lithologic structure and evolution of this active continental rift and provide constraints on various tectonic models of the continental rift.