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Rupture process of the April 2017 Mw 6.5 Botswana Earthquake: deepest earthquake observed in continental Africa

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Abstract

On April 3, 2017, an earthquake of magnitude Mw 6.5 ruptured in Botswana in a region where there was no significant recent tectonic activity and where present-day deformation is believed to be negligible. The event was followed by several aftershocks distributed along NW-SE direction with NE-SW extension direction. We focused on the determination of reliable source parameters for the Mw 6.5 main shock using moment tensor inversion, in both time and frequency domains from regional, broadband waveform data. We retrieve the source depth at 38.4 km, probably the deepest earthquake observed in continental Africa. The estimated hypocentral depth of this earthquake is roughly about the Moho depth beneath the region, reflecting a deep source that is relatively rare in stable continental regions. The result may suggest that the seismogenic depth is as deep as the average global Moho thickness indicating the upper mantle and lower crust region is actively deforming due to a reactivation of the preexisting fault oriented in the NW-SE direction. The resulting focal mechanism of the event shows normal faulting with NE-SW extension direction. The result may provide useful information for contemporary geodynamic investigation of the area.

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Acknowledgements

We acknowledge Incorporated Research Institutions for Seismology (IRIS) for making the data freely available. The manuscript has benefited a lot from helpful and constructive comments from the three anonymous reviewers.

Funding

This work is funded by the UNISCO IGCP-659 grant. We received financial support to attend the 2nd CAJG from Professor Mustapha Meghraoui.

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Authors and Affiliations

  1. School of Earth Sciences, Addis Ababa University, Box 1176, Addis Ababa, Ethiopia

    Jima Asefa

  2. College of Natural and Computational Sciences, Wolkite University, Box 07, Wolkite, Ethiopia

    Jima Asefa

  3. Institute of Geophysics, Space Science and Astronomy, Addis Ababa University, Box 1176, Addis Ababa, Ethiopia

    Atalay Ayele

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  1. Jima Asefa
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Correspondence to Jima Asefa.

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Responsible Editor: Mustapha Meghraoui

This article is part of the Topical Collection on Seismic Hazard and Risk in Africa

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Asefa, J., Ayele, A. Rupture process of the April 2017 Mw 6.5 Botswana Earthquake: deepest earthquake observed in continental Africa. Arab J Geosci 14, 823 (2021). https://doi.org/10.1007/s12517-021-06890-1

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