Continental breakup on the East African Rift
Academic Affiliation: University of Texas at El Paso
Science Research Mentors: Eric Calais, Purdue University, David Phillips, UNAVCO
Stephen Hernández who had just completed his junior year at the University of Texas at El Paso returned to Boulder for his second year as a RESESS protégé. Stephen had an unusual project this year. He worked with David Phillips of UNAVCO to learn processing of high precision GPS data during the regular summer RESESS program and then accompanied Dr. Eric Calais of Purdue University on a field season in Tanzania to obtain GPS data in a small portion of the East African Rift. A crew of scientists, a UNAVCO field engineer, and students from the U.S. joined Tanzanian scientists and support staff for three weeks of installing short term GPS instrumentation. Stephen's abstract explains that the exact direction and distribution of strain across the East African Rift plate boundary zone remains a mystery due to inadequate data and analysis of the rift. After returning from Africa, Stephen continues to work on taking the raw data from the summer field work and refining it to obtain extremely precise GPS data points which will be used to determine the amount and direction of crustal movement in the field area.
Although the East African Rift (EAR) is often cited as the premier example of incipient rifting, the shear size and oft times inaccessibility of the rift have limited the analysis and interpretation for accurate determination of the physical processes controlling the deformation of the Earth's crust. Existing geodetic data are wholly inadequate to address the direction and distribution of extensional strain along and across this incipient plate boundary zone. A new five-year project with three Global Positioning System (GPS) campaigns (in years 1, 3, and 5) distributed across Tanzania will help us obtain interpretable results with a total extension rate across the EAR on the order of 5 mm yr-1. GPS measurements in the EAR are critical to finally establish the kinematic framework of rifting. New GPS measurements spanning the Western and Eastern rifts in Tanzania, combined with the distant data on the surrounding plates, will provide the kinematics of deformation across and along the length of the EAR. In particular, they will allow us to test and further refine the counter clockwise rotation model of the Tanzanian craton suggested by the very scarce geodetic data currently available. GPS measurements will also provide strain distribution across and along the Western and Eastern rifts. In addition to horizontal motions, GPS measurements will provide vertical displacements, critical to test for present-day uplift of the African plateau predicted from the African Superplume upwelling. Using the GAMIT/GLOBK suite of GPS processing software, we present a new, preliminary determination of the horizontal velocities in the EAR at Tanzanian latitudes.