Collaborative Research: The context for rifting in East Africa - melt distribution and lithospheric removal imaged from axis to flank

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Continental rifting is a fundamental part of the plate tectonic cycle, and lies at the nexus of geothermal and mineral resources, seismic and volcanic hazards, and geophysical research. Substantial variation between rift zones worldwide indicates that continental breakup is dictated by a complex interplay of tectonic forces and geologic characteristics. Therefore, it is critical to understand the full context for a rifting system, from the highly extended rift center that houses volcanoes and earthquakes to the flanks of the rift, where extension is just beginning and pre-rift structures are still evident. The Main Ethiopian Rift segment of the East Africa rift is perhaps the world's most iconic continental rift. New imaging techniques will be applied to recently acquired seismic data spanning this rift to reveal the 3-D internal structure of this rift and shed light on key geologic processes in this and other rifts around the world. This project involves collaboration with scientists from Ethiopia and provides career opportunities for early career researchers under-represented in the Earth sciences. Detailed imaging of the internal structure of an entire rift system, from flank to axis, can shed light on the mechanics, controls, and time-dependency of extensional processes in the Main Ethiopian Rift. Recently acquired data from a wide aperture broadband seismic array is critical in sampling pre-rifted structure that may control rift dynamics, as well as to image the geodynamically crucial transitional zone between rift axis and flank. Our tomographic technique entails simultaneous inversion of P and S receiver functions with Rayleigh wave phase velocities within a Bayesian framework; this approach is ideally suited to capture lithologic/seismic discontinuities, the presence of melt, and complex 3-D rift structure. Anisotropic body wave inversions and splitting studies will help constrain the locus of melt as well as the time-integrated strain history of this rift. This project utilizes seismic data from a number of previous projects in the region, combining the strengths of multiple deployments to achieve a synoptic understanding. Collaboration with Ethiopian scientists and supporting the early careers of under-represented researchers are among the broader impacts of this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.