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Seismicity During Continental Breakup in the Red Sea Rift of Northern Afar

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)2345-2362
Number of pages18
JournalJournal of Geophysical Research: Solid Earth
Volume123
Issue number3
Early online date23 Mar 2018
DOIs
DateAccepted/In press - 24 Feb 2018
DateE-pub ahead of print - 23 Mar 2018
DatePublished (current) - Mar 2018

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 subaerially. Between February 2011 and February 2013 two seismic networks were installed in Ethiopia and Eritrea. We locate 4,951 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.

    Research areas

  • Afar, Continental Rifting, East Africa, Seismicity, Volcanic Seismicity

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via Wiley at https://doi.org/10.1002/2017JB014902 . Please refer to any applicable terms of use of the publisher.

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    Licence: CC BY

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