State of stress and stress rotations: Quantifying the role of surface topography and subsurface density contrasts in magmatic rift zones (Eastern Rift, Africa)

In rift settings, the crustal stress field is dominated by extension, which leads to rift-parallel topography and basin alignments. However in some continental rift systems, some observables of the orientation of principal stresses show substantial deviations from these patterns. Such stress field rotations are currently poorly understood and could reflect the critical role of rift magmatism in the creation of topography, the plate state-of-stress, and volcanic and tectonic processes. Yet the role of magma intrusions, crustal thinning, and rift basin and flank topography on rift zone stress field rotations remain poorly quantified. The seismically- and volcanically-active Magadi-Natron-Manyara region of the East African Rift shows a 60∘ local stress field rotation with respect to regional extension. Here, we test the hypothesis that such rotation is due to the cumulative effects of surface and subsurface loads (lateral subsurface density contrasts). We use analytical and calibrated numerical models of magmatic rift zones to simulate lithospheric deformation in the presence of magma bodies, crustal thinning, and topography to quantify their effect on intrusions and fault kinematics in a rift setting. Our 3D static models of a weakly extended rift suggest that surface topography influences shallow stress localization, whereas subsurface density contrasts play a larger role in lower crustal stress localization. Both patterns suggest a preferred region for melt storage beneath the rift valley. We show that the interaction between topography, crustal thinning, extension, and a pressurized magma reservoir could generate principal stress orientations consistent with the local stress rotation observed from earthquake focal mechanisms. Our results demonstrate how rift topography and the geometry of crustal thinning can guide magmatism and strain localization, highlighting the need for a three-dimensional treatment of rift kinematics.

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Work Title State of stress and stress rotations: Quantifying the role of surface topography and subsurface density contrasts in magmatic rift zones (Eastern Rift, Africa)
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Open Access
Creators
  1. Sarah Jaye Oliva
  2. Cynthia J. Ebinger
  3. Eleonora Rivalta
  4. Charles A. Williams
  5. Christelle Wauthier
  6. Claire A. Currie
Keyword
  1. Rift
  2. Continental rifting
  3. Tectonics
  4. Stress
  5. Topography
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Earth and Planetary Science Letters
Publication Date March 21, 2022
Publisher Identifier (DOI)
  1. https://doi.org/10.1016/j.epsl.2022.117478
Deposited July 21, 2022

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Version 1
published

  • Created
  • Added Preprint_OlivaEPSL2022_withSupp.pdf
  • Added Creator Sarah Jaye Oliva
  • Added Creator Cynthia J. Ebinger
  • Added Creator Eleonora Rivalta
  • Added Creator Charles A. Williams
  • Added Creator Christelle Wauthier
  • Added Creator Claire A. Currie
  • Published
  • Updated Work Title, Keyword, Subtitle, and 1 more Show Changes
    Work Title
    • State of stress and stress rotations
    • State of stress and stress rotations: Quantifying the role of surface topography and subsurface density contrasts in magmatic rift zones (Eastern Rift, Africa)
    Keyword
    • Rift, Continental rifting, Tectonics, Stress, Topography
    Subtitle
    • Quantifying the role of surface topography and subsurface density contrasts in magmatic rift zones (Eastern Rift, Africa)
    Publication Date
    • 2022-04-15
    • 2022-03-21