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    Seismicity during continental breakup in the Red Sea rift of Northern Afar

    Illsley-Kemp, F. and Keir, D. and Bull, J.M. and Gernon, T.M. and Ebinger, C. and Ayele, A. and Hammond, James O.S. and Kendall, J-M. and Goitom, B. and Belachew, M. (2018) Seismicity during continental breakup in the Red Sea rift of Northern Afar. Journal of Geophysical Research: Solid Earth 123 (3), pp. 2345-2362. ISSN 2169-9313.

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    Abstract

    Continental rifting is a fundamental component of plate tectonics. Recent studies have highlighted the importance of magmatic activity in accommodating extension during late‐stage rifting, yet the mechanisms by which crustal thinning occurs are less clear. The Red Sea rift in Northern Afar presents an opportunity to study the final stages of continental rifting as these active processes are exposed sub‐aerially. Between February 2011 and February 2013 two seismic networks were installed in Ethiopia and Eritrea. We locate 4951 earthquakes, classify them by frequency content and calculate 31 focal mechanisms. Results show that seismicity is focused at the rift axis and the western marginal graben. Rift axis seismicity accounts for ∼64% of the seismic moment release and exhibits a swarm‐like behavior. In contrast, seismicity at the marginal graben is characterized by high‐frequency earthquakes that occur at a constant rate. Results suggest that the rift axis remains the primary locus of seismicity. Low frequency earthquakes, indicative of magmatic activity, highlight the presence of a magma complex ∼12 km beneath Alu‐Dalafilla at the rift axis. Seismicity at the marginal graben predominantly occurs on westward dipping, antithetic faults. Focal mechanisms show that this seismicity is accommodating E‐W extension. We suggest that the seismic activity at the marginal graben is either caused by upper crustal faulting accommodating enhanced crustal thinning beneath Northern Afar, or as a result of flexural faulting between the rift and plateau. This seismicity is occurring in conjunction with magmatic extension at the rift axis, which accommodates the majority of long‐term extension.

    Metadata

    Item Type: Article
    Additional Information: Accepted for publication. Copyright American Geophysical Union. Further reproduction or electronic distribution is not permitted.
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences > UCL/Birkbeck Centre for Planetary Sciences
    Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: James Hammond
    Date Deposited: 19 Mar 2018 14:28
    Last Modified: 19 Aug 2019 09:04
    URI: http://eprints.bbk.ac.uk/id/eprint/21708

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