Browsing by Author "Naliboff, John"

Now showing 1 - 2 of 2
  • Thumbnail Image
    A Geodynamic Investigation of Plume-Lithosphere Interactions Beneath the East African Rift
    Rajaonarison, Tahiry A.; Stamps, D. Sarah; Naliboff, John; Nyblade, Andrew; Njinju, Emmanuel A. (American Geophysical Union, 2023-04)
    The force balance that drives and maintains continental rifting to breakup is poorly understood. The East African Rift (EAR) provides an ideal natural laboratory to elucidate the relative role of plate driving forces as only lithospheric buoyancy forces and horizontal mantle tractions act on the system. Here, we employ high-resolution 3D thermomechanical models to test whether: (a) the anomalous, rift-parallel surface deformation observed by Global Navigation Satellite System (GNSS) data in the EAR are driven by viscous coupling to northward mantle flow associated with the African Superplume, and (b) the African Superplume is the dominant source mechanism of anomalous rift-parallel seismic anisotropy beneath the EAR. We calculate Lattice Preferred Orientations (LPO) and surface deformation from two types of mantle flow: (a) a scenario with multiple plumes constrained by shear wave tomography and (b) a single superplume model with northward boundary condition to simulate large-scale flow. Comparison of calculated LPO with observed seismic anisotropy, and surface velocities with GNSS and plate kinematics reveal that there is a better fit with the superplume mantle flow model, rather than the tomography-based (multiple plumes) model. We also find a relatively better fit spatially between observed seismic anisotropy and calculated LPO with the superplume model beneath northern and central EAR, where the superplume is proposed to be shallowest. Our results suggest that the viscous coupling of the lithosphere to northward mantle flow associated with the African Superplume drives most of the rift-parallel deformation and is the dominant source of the first-order pattern of the observed seismic anisotropy in the EAR.
  • Thumbnail Image
    Role of Lithospheric Buoyancy Forces in Driving Deformation in East Africa From 3D Geodynamic Modeling
    Rajaonarison, Tahiry A.; Stamps, D. Sarah; Naliboff, John (2021-03-28)
    Despite decades of investigation, the origin of forces driving continental rifting remains highly debated. Deciphering their relative contributions is challenging due to the nonlinear and depth-dependent nature of lithospheric rheology. Recent geodynamic studies of the East African Rift (EAR) report contradicting results regarding the relative contribution of horizontal mantle tractions and lithospheric buoyancy forces. Here, we use high-resolution 3D regional numerical modeling of the EAR to isolate the contribution lithospheric buoyancy forces to observed deformation. Modeled surface velocities closely match kinematic models of the Somalian Plate, Victoria Block, and Rovuma Block motions, but provide poor fit to along-rift surface motions in deforming zones. These results suggest that lithospheric buoyancy forces primarily drive present-day similar to E-W extension across the EAR, but intrarift deformation may result from viscous coupling to horizontal asthenospheric flow.