Imaging Lithospheric Discontinuities Beneath the Northern East African Rift Using S-to-P Receiver Functions

Area of Science:

• Geophysics
• Tectonics
• Lithospheric structure imaging

Background:

• Continental rifting involves lithospheric stretching, thinning, and heating.
• The East African Rift system provides a unique setting to study the transition from continental rifting to seafloor spreading.
• Understanding lithospheric processes is crucial for deciphering rift evolution.

Purpose of the Study:

• To image the lithospheric structure beneath the northern East African Rift system.
• To investigate the nature of the lithosphere-asthenosphere boundary (LAB) in a region of active rifting.
• To understand the role of melt in lithospheric thinning during continental rifting.

Main Methods:

• Utilized S-to-P receiver functions to analyze seismic wave propagation.
• Applied waveform modeling to interpret seismic data.
• Investigated seismic velocity structures and phase arrivals.

Main Results:

• Mapped the Moho depth at approximately 31 km beneath the Ethiopian plateau.
• Determined crustal thickness variations, thinning from 28 km in the Main Ethiopian rift to 23 km in northern Afar.
• Identified a lithosphere-asthenosphere boundary (LAB) at 67 km depth beneath the plateau, characterized by a velocity decrease likely due to partial melt.
• Observed a lack of a distinct LAB phase beneath the rift zone.

Conclusions:

• The lithosphere-asthenosphere boundary beneath the Ethiopian plateau is likely defined by partial melt.
• The absence of a LAB phase beneath the rift suggests melt percolation through the lithosphere's base.
• These findings provide insights into the dynamic processes occurring during continental rifting and incipient seafloor spreading.