A team of University of Colorado at Boulder geophysicists is leading a study funded by the National Science Foundation to precisely measure the ground movement and earthquake potential of the Rio Grande Rift in Colorado and New Mexico.
Using state-of-the-art Global Positioning System instruments at 24 sites in Colorado and New Mexico, the research team will track the rift's movement in millimeters during most of the next three years. The study will provide unprecedented data about the volcanically active region.
"The Rio Grande Rift extends hundreds of miles from Colorado's central Rocky Mountains to Mexico, and geologists have estimated it spreads apart up to five millimeters each year," said geological sciences Associate Professor Anne Sheehan, who leads the project. "However, the margin of error in these estimates can be nearly as much as the estimates themselves.
"Our project will determine exact rates of movement along the rift, and assess the earthquake hazards it poses," said Sheehan, who also is affiliated with CU-Boulder's Cooperative Institute for Research in Environmental Sciences. She is joined on the project by Associate Professor Steve Nerem of aerospace engineering and research associate Tony Lowry of physics.
The northern Rio Grande River follows through the rift valley, where magma from the Earth's mantle rises to the surface along the rift. The rising molten rock causes a spreading motion in the crust and the creation of long, fault-bounded basins that are susceptible to earthquakes. Some geologists think that in a few million years, the area will become a new ocean basin.
"A better understanding of the variable character of the rift could help us understand how and why tectonic plates undergo stretching, as well as the earthquake and volcanic hazards within rift zones," Sheehan said.
The team will compare their measured rates of motion with all other available data, including seismic velocities in the crust and mantle, gravity and surface heat flow. The data will be combined to build computer models of the processes that control how tectonic plates undergo rifting.
"An intriguing possibility is that stretching in the Rio Grande Rift is heterogeneous, with different processes operating in the crust and the mantle," Sheehan said. "Available geologic observations also suggest that the character of the rifting changes dramatically from north to south."
Another primary goal of the project is to understand what stretching rates measured at the surface imply about the stretching of the plate at deeper levels.
The research team is comprised of scientists and students at CU-Boulder and the University of New Mexico. Graduate and undergraduate students will be trained in GPS measurement and analysis as part of the project.
CU-Boulder students also will work on educational outreach related to the project such as training for K-12 schoolteachers and involving middle schools in the "adoption" of GPS sites. They also will promote interaction with agencies interested in earthquake and volcanic hazards along the Rio Grande Rift including state geological surveys, local and federal emergency management agencies, local governments, city planners and engineers.
The project is part of NSF's EarthScope initiative, a partnership with the U.S. Geological Survey and NASA to study North American geologic evolution, earthquakes and volcanic activity.
For more information on the Rio Grande Rift project visit