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The decade-long Machaze-Zinave aftershock sequence in the slowly straining Mozambique Rift

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Original languageEnglish
Pages (from-to)504-531
Number of pages28
JournalGeophysical Journal International
Volume217
Issue number1
Early online date22 Jan 2019
DOIs
DateAccepted/In press - 14 Jan 2019
DateE-pub ahead of print - 22 Jan 2019
DatePublished (current) - 1 Apr 2019

Abstract

Southern Mozambique is the southernmost expression of the continental East African Rift. Here, extension rates are low and rifting is achieved through normal faulting. Incipient rift environments provide an ideal location to investigate the role of reactivated pre-existing structures, aftershock sequences, and fault interactions in rift development. In 2016 a Mw 5.6 earthquake occurred in the Zinave region of southern Mozambique, ∼10 km south-east of the Mw 7.0 2006 Machaze earthquake. We reanalyse ENVISAT InSAR observations of the Machaze earthquake, together with new Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) observations of the Zinave earthquake, and solve for uniform and distributed slip models for both events. We find the Machaze earthquake occurred on a steeply dipping (∼75◦) fault, in agreement with other studies, but that the Zinave earthquake occurred on a ∼60◦ dipping fault. The occurrence of the Zinave earthquake at the same depth as afterslip following the Machaze earthquake suggests laterally heterogeneous crustal frictional properties. The Machaze earthquake caused a Coulomb stress increase of ∼0.2 MPa on the Zinave fault. The full >10 year record of seismicity following the Machaze event can be fit by the Omori law, showing that the Zinave earthquake is part of a decade-long aftershock sequence, consistent with long-duration aftershock sequences in other slowly straining regions. Aftershocks represent a major hazard that needs to be considered if a large earthquake were to occur in the southern East African Rift system today.

    Research areas

  • Earthquakes, Fault Slip, Aftershocks, Rifts, Tectonics, Mozambique

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    Rights statement: This is the final published version of the article (version of record). It first appeared online via Oxford University Press at https://academic.oup.com/gji/article/217/1/504/5298869?searchresult=1. Please refer to any applicable terms of use of the publisher.

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