EGU21-5599, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-5599
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seismotectonic Analysis of the 2017 Moiyabana Earthquake (MW 6.5; Botswana), Insights from field investigations, aftershock and InSAR studies 

Thifhelimbilu Mulabisana1,2,5, Mustapha Meghraoui1, Vunganai Midzi2, Mohamed Saleh3, Onkgopotse Ntibinyane4, Motsamai Tarzan Kwadiba4, Brassnavy Manzunzu2, Oarabile Seiphemo4, Tebogo Pule2, and Ian Saunders2
Thifhelimbilu Mulabisana et al.
  • 1University of Strasbourg, EOST - ITES, DA, Strasbourg, France (mulabisana@etu.unistra.fr)
  • 2Council for Geoscience, Pretoria, South Africa
  • 3NRIAG, Helwan, Egypt
  • 4Botswana Geoscience Institute, Lobatse, Botswana
  • 5Nelson Mandela University, Port Elizabeth, South Africa

The 3 April 2017 MW 6.5, Moiyabana (Botswana) earthquake occurred in the continental interior of the African plate and in a seismogenic region previously considered as stable. We analyse the mainshock and aftershock sequence based on a local seismic network and local seismotectonic characteristics. The earthquake rupture geometry is constrained with more than 1,000 aftershocks recorded over a period of three months and from the InSAR analysis of Sentinel-1 images (ascending orbit). The mainshock (25.134 E, 22.565 S; depth 22 ± 3 km) was followed by more than 500 events of magnitude M ≥ 0.8 recorded in April 2017 including the largest aftershock (MW 4.6 on the 5 April 2017). Focal mechanism solutions of the mainshock and aftershocks display predominance of NW-SE trending and NE dipping normal faulting. Stress inversion of focal mechanisms obtained from the mainshock and aftershock database are compatible with a NE-SW extension under normal faulting regime. The InSAR study shows fringes with two lobes with 4 to 6 cm coseismic slip on a NW-SE elongated and 30-km-long surface deformation consistent with the mainshock location and normal faulting mechanism. The modelling of surface deformation provides the earthquake rupture dimension at depth with ~ 1 m maximum slip on a fault plane striking 315°, dipping 45°, -80° rake and with Mo 7.12 1018 Nm Although the seismic strain rate is of low level, the occurrence of the 2017 Moiyabana earthquake, followed by an aftershock sequence in the central Limpopo belt classifies the intraplate region as an active plate interior. 

How to cite: Mulabisana, T., Meghraoui, M., Midzi, V., Saleh, M., Ntibinyane, O., Kwadiba, M. T., Manzunzu, B., Seiphemo, O., Pule, T., and Saunders, I.: Seismotectonic Analysis of the 2017 Moiyabana Earthquake (MW 6.5; Botswana), Insights from field investigations, aftershock and InSAR studies , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5599, https://doi.org/10.5194/egusphere-egu21-5599, 2021.

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