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Journal Article

Mechanism for deep crustal seismicity: Insight from modeling of deformation process at the Main Ethiopian Rift

Authors
/persons/resource/ameha

Muluneh,  Ameha A.
2.5 Geodynamic Modelling, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

/persons/resource/brune

Brune,  Sascha
2.5 Geodynamic Modelling, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Illsley‐Kemp,  Finnigan
External Organizations;

Corti,  Giacomo
External Organizations;

Keir,  Derek
External Organizations;

/persons/resource/acglerum

Glerum,  A.
2.5 Geodynamic Modelling, 2.0 Geophysics, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;
3.1 Inorganic and Isotope Geochemistry, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Kidane,  Tesfaye
External Organizations;

Mori,  Jim
External Organizations;

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Fulltext (public)

5002333.pdf
(Publisher version), 8MB

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Citation

Muluneh, A. A., Brune, S., Illsley‐Kemp, F., Corti, G., Keir, D., Glerum, A., Kidane, T., Mori, J. (2020): Mechanism for deep crustal seismicity: Insight from modeling of deformation process at the Main Ethiopian Rift. - Geochemistry Geophysics Geosystems (G3), 21, 7, e2020GC008935.
https://doi.org/10.1029/2020GC008935


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5002333
Abstract
We combine numerical modeling of lithospheric extension with analysis of seismic moment release and earthquake b‐value in order to elucidate the mechanism for deep crustal seismicity and seismic swarms in the Main Ethiopian Rift (MER). We run 2D numerical simulations of lithospheric deformation calibrated by appropriate rheology and extensional history of the MER to simulate migration of deformation from mid‐Miocene border faults to ~30 km wide zone of Pliocene to recent rift floor faults. While the highest strain rate is localized in a narrow zone within the rift axis, brittle strain has been accumulated in a wide region of the rift. The magnitude of deviatoric stress shows strong variation with depth. The uppermost crust deforms with maximum stress of 80 MPa, at 8‐14 km depth stress sharply decreases to 10 MPa and then increases to a maximum of 160 MPa at ~18 km depth. These 2 peaks at which the crust deforms with maximum stress of 80 MPa or above correspond to peaks in the seismic moment release. Correspondingly, the drop in stress at 8‐14 km correlates to a low in seismic moment release. At this depth range, the crust is weaker and deformation is mainly accommodated in a ductile manner. We therefore see a good correlation between depths at which the crust is strong and elevated seismic deformation, while regions where the crust is weaker deform more aseismically. Overall the bimodal depth distribution of seismic moment release is best explained by rheology of the deforming crust.