Advanced seismic tomography methods were used to image the top 200 miles of Earth’s mantle layer beneath the African continent with higher resolution than traditional seismic tomography approaches.  These high-resolution images allow us to have a better understanding of where unusually warm and ductile mantle rocks are connected under the volcanically and seismically active East African Rift System.  Additionally, these imaging methods help us to better understand how this warm and buoyant mantle material flows around ancient, strong and stable continental blocks called cratons.  From this study, we learn more about how these cratons might influence where rifts and their associated hazards develop within the center of continents.  These high-resolution, 3D maps of African Earth structure are also useful for more accurately understanding earthquakes and the faults that they rupture in this region.

This research used a unique dataset obtained from existing records of long-period, random noise from hundreds of seismometers installed throughout the African continent during the past 25+ years.  Using this unique long-period ambient noise dataset and the high performance computing facilities at the University of Rhode Island, African Earth structure was imaged at high resolution. The results of the project show that the Congo Craton, which was previously thought to be one large continuous and rigid block may actually be two smaller blocks separated by a slightly weaker region where deformation may have occurred in the geologically distant past.  This separation of the two cratonic blocks may influence how warm/buoyant mantle rocks are diverted towards the active East African Rift System.  The results also suggest possible separation between two large regions of warm/weak upper mantle rocks directly under the East African Rift System.  This provides additional insight into how the weak mantle rocks flow beneath this region as well as their possible effects on patterns of volcanism and deformation at the surface of the Earth.  In addition to what has been learned about the Congo Craton and the East African Rift System, the results also show regions of warm material within the upper mantle beneath North Africa, where two volcanic plateaus are located.  Because very few seismometers have been installed throughout North Africa, the results provide new information about regions where less is known about the deeper Earth structure. These tomographic images have been presented at geologic and geophysical conferences during the previous year, and are being finalized for publication.  The results will help to inform future African Earth science research through the Incorporated Research Institutions for Seismology (IRIS) Earth Model Collaboration website.

In addition to the scientific merit of the project, this project also supported the educational aims of the Africa Array summer geophysics program offered through the Pennsylvania State University in collaboration with the University of the Witswatersrand in South Africa.  As part of this program the principle investigator worked during two summers (2014 and 2015) to teach geophysical methods to students from groups underrepresented in the geosciences.  Students learned geophysical field techniques and were mentored by the principal investigator as well as others from Penn State University and the University of Witswatersrand regarding careers in geophysics and Earth science.  They were also taught about how to apply to and succeed in graduate school.  The educational materials produced during this period were passed along to the future instructors of the program.

Last Modified: 06/19/2016
Modified by: Erica L Emry