The 03 April 2017 Botswana M6.5 earthquake: Preliminary results

Midzi, V.; Saunders, Ian; Manzunzu, B.; Kwadiba, M. T. O.; Jele, V.; Mantsha, R.; Marimira, Kwangwari T.; Mulabisana, T.; Ntibinyane, Onkgopotse; Pule, T.; Rathod, Ganesh W.; Sitali, M.; Tabane, L.; Aswegen, G. van; Zulu, B.S.

doi:10.1016/j.jafrearsci.2018.03.027

Cited by 21 publications

(30 citation statements)

References 18 publications

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“…The earthquake was a normal faulting event in the lower crust, close and parallel to the border of the Kaapvaal craton (Materna et al, ; Midzi et al, ; Moorkamp et al, ; Kolawole et al, ). Here, we suggest that it is associated to the EARS, where the low‐velocity zone acts as a conduit of fluids or melt from the low‐velocity mantle, activating brittle failure in the crust.…”

Section: Resultsmentioning

confidence: 99%

Crustal and Upper Mantle Shear Wave Velocity Structure of Botswana: The 3 April 2017 Central Botswana Earthquake Linked to the East African Rift System

Fadel

Paulssen

Meijde

et al. 2020

Geophysical Research Letters

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Rayleigh wave group and phase velocity measurements obtained from ambient noise and earthquake data at 51 broadband stations were used to construct the first 3‐D crustal and upper mantle shear wave velocity model of Botswana. The model shows low crustal velocities associated with the Passarge and Nosop sedimentary basins, whereas the Kaapvaal, Zimbabwe, Maltahohe, and Congo Cratons are recognized by high mantle velocities. The lowest upper mantle shear wave velocity, beneath northeastern Botswana, is associated with the southwestern branch of the East African Rift System. This low‐velocity mantle anomaly appears to be linked to the crust of the Okavango Rift Zone and the location of the 3 April 2017 Mw 6.5 earthquake in central Botswana. We suggest that fluids or melt at the base of the crust from the southward continuation of the East African Rift Zone triggered the intraplate earthquake in an extensional tectonic setting.

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Section: Resultsmentioning

confidence: 99%

Crustal and Upper Mantle Shear Wave Velocity Structure of Botswana: The 3 April 2017 Central Botswana Earthquake Linked to the East African Rift System

Fadel

Paulssen

Meijde

et al. 2020

Geophysical Research Letters

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“…This finding suggests that the faulting that might have happened in the region near the epicentre of the 6.5 magnitude would be linked to some existing fault in the region having the same orientation (some north-westerly fault that was not mapped earlier). The investigation by Midzi et al [19] on the distributions of locations of aftershocks of this earthquake exhibited a north west-south east orientation in two clusters closer to the epicentre extending for about 25 km and 19 km in length. These observations also support the existence of some fault development in a north west-south east orientation close to the locations of this earthquake.…”

Section: Examination Of the Earthquake Location With The Existing Seismotectonic Mapmentioning

confidence: 78%

Mapping of Surface Deformation and Displacement Associated with the 6.5 Magnitude Botswana Earthquake of 3 April 2017 Using DInSAR Analysis

Thomas

2020

GaEE

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The DInSAR analysis was performed for mapping surface deformation and displacement associated with the 6.5 magnitude Botswana earthquake of 3 April 2017 using Sentinel‑1 data and SNAP. The analyses involved: coregistration of SAR images, interferogram formation, debursting, merging of sub‑swaths, topographic phase removal, phase filtering, phase unwrapping, orthorectification and calculation of vertical displacement for two situations (unmasked and masked with a layer of coherence ≥0.6). The vertical displacement for the unmasked situation ranged from −122 mm to +136 mm whereas in the masked layer it ranged from −84 mm to +122 mm. Negative surface deformation (subsidence) is seen in the epicentre region and eastern, north‑eastern, northern areas of the image whereas major positive surface deformations (uplift) are seen in the south‑western, western and north‑western corner part. Comparison of displacements with geology revealed that major deformation occurred in the Karoo basalts and lesser surface deformation has occurred in the Lebung Group rocks of the northern, NE and SW region. The elongated shape of deformation near the epicentre and positive vertical displacement seen towards the SW of the epicentre and negative vertical displacement seen towards NE of the epicentre reveals that the region has undergone uplifting and subsidence on either side of the area close to the epicentre (similar to faulting in a NW or SE direction). The boundaries of the uplift and subsidence regions inferred as long lineaments were digitised as faults. Comparison of the deformation with existing seismotectonic map revealed the existence of some north‑westerly faults seen in the region.

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“…The spatial distribution of aftershocks in Figure 5 shows that most aftershocks are trending in a northwest-southeast direction and this probably indicates the rupture plane of the Moiyabana earthquake. A previous study by [10] suggests that two fault planes link the mainshock and the aftershocks. In addition, most aftershocks mainly lie within the Limpopo mobile belt that is sandwiched between the Kaapvaal craton to the south and Zimbabwe craton to the north.…”

Section: Discussionmentioning

confidence: 91%

“…The Kaapvaal and Zimbabwe cratons are sutured together by the Archean and Paleoproterozoic Limpopo belt. This belt was the result of the collision of these two cratons and it is associated with highly metamorphosed granite-greenstone and granulite terranes [10]. Limpopo belt is subdivided into four tectonic zones which are the western, northern, central and southern marginal zones.…”

Section: Brief Geology Of Botswanamentioning

confidence: 99%

“…These cratons are old and stable parts of the continental lithosphere and Archean rocks are the oldest rocks known on Earth [17]. Earthquakes with a magnitude greater than 7 are rare across southern Africa and seismic activity in southern Africa is mostly associated with the East African Rift System (EARS) [10]. Before 1949, Botswana was not recognized of having any seismic activity because there were no seismic networks to monitor seismic activity in Botswana.…”

Section: Seismicity Of Botswanamentioning

confidence: 99%

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Some Foreshocks and Aftershocks Associated with the Moiyabana Earthquake of 2017 in Botswana

Olebetse¹,

Mmese²,

Simon³

et al. 2020

IJG

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On the 3 rd of April 2017, an earthquake of moment magnitude 6.5 occurred near Moiyabana in central Botswana. This paper is aimed at studying the spatial distribution of the foreshock and aftershock sequences associated with the Moiyabana earthquake. The foreshocks and aftershocks data used were from the Botswana Geoscience Institute (BGI) and the Seisan software was used to analyze the foreshock and aftershock events. The analyses revealed nine epicenter locations of foreshocks which are spread out across the country and most of them are located in the central and southern parts of Botswana, while the aftershocks are clustered around the mainshock. Although five of the nine foreshocks occurred far from the boundaries of major tectonic units, the other four occurred near key features such as the Zoetfontein, Lecha and Chobe faults. The spatial distribution of aftershocks indicates that the stress released by the mainshock, reactivated the planes of weakness in the vicinity of the mainshock and farther away from the mainshock. Hence, this affected the Zoetfontein fault, the boundary between Passarge basin and Magondi belt and the boundary between the Kaapvaal craton and Limpopo mobile belt. The aftershocks also show a northwest-southeast trend, which probably indicates the rupture plane; and mainly lie within the Limpopo mobile belt that is sandwiched between the Kaapvaal craton to the south and Zimbabwe craton to the north. Furthermore, the aftershocks concentration to the south reveals a close relation in demarcating the boundary of the Kaapvaal craton and the Limpopo mobile belt.

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The 03 April 2017 Botswana M6.5 earthquake: Preliminary results

Cited by 21 publications

References 18 publications

Crustal and Upper Mantle Shear Wave Velocity Structure of Botswana: The 3 April 2017 Central Botswana Earthquake Linked to the East African Rift System

Crustal and Upper Mantle Shear Wave Velocity Structure of Botswana: The 3 April 2017 Central Botswana Earthquake Linked to the East African Rift System

Mapping of Surface Deformation and Displacement Associated with the 6.5 Magnitude Botswana Earthquake of 3 April 2017 Using DInSAR Analysis

Some Foreshocks and Aftershocks Associated with the Moiyabana Earthquake of 2017 in Botswana

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