Seismotectonic analysis of the 2017 moiyabana earthquake (MW 6.5; Botswana), insights from field investigations, aftershock and InSAR studies

Mulabisana, T.; Meghraoui, Mustapha; Midzi, V.; Saleh, Mohamed; Ntibinyane, Onkgopotse; Kwadiba, T.; Manzunzu, B.; Seiphemo, Oarabile; Pule, T.; Saunders, Ian

doi:10.1016/j.jafrearsci.2021.104297

Cited by 6 publications

(6 citation statements)

References 63 publications

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“…The yellow dashed normal fault symbol is inferred from the 2017 Moiyabana M W 6.5 earthquake by Mulabisana et al. (2021). The yellow dashed line corresponds to the ridge of the Kalahari Schwelle.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, most of the seismicity in the Makgadikgadi Basin is located in its southern part and cannot be correlated to the faults of the MRZ. Most events have a magnitude <4 and cluster around mining areas, whereas the 2017 Mw 6.5 earthquake, located more than 100 km further south, is correlated to the reactivation of NW‐SE Neoproterozoic faults related to the Zoetfontain Faults System (Kolawole et al., 2017; Mulabisana et al., 2021; Paulssen et al., 2022).…”

Section: Discussionmentioning

confidence: 99%

“…A magnitude 6.5 earthquake affected this area in 2017. The focal mechanism suggests a NE dipping normal fault striking NW‐SE almost orthogonal to the main trend of the MRZ and of the Okavango Graben (Kolawole et al., 2017; Mulabisana et al., 2021). Most of the seismicity in the Makgadikgadi Basin has been detected after 2004, leading some authors to suggest that a measurement bias resulted in underestimating the seismic activity in this region compared to others, such as the Okavango Graben (Nthaba et al., 2018; Pastier et al., 2017).…”

Section: Geological and Geomorphological Settingsmentioning

confidence: 99%

“…Seismic data come from International Seismological Centre (2022). The focal mechanism indicates the 2017 Mw 6.5 Moiyabana earthquake (Mulabisana et al., 2021). For (a) and (b) faults are compiled and modified from Chorowicz (2005), Daly et al.…”

Section: Introductionmentioning

confidence: 99%

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Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Gaudaré,

Dauteuil,

Jolivet

2024

Tectonics

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The Southwestern Branch of the East African Rift System propagates through the Central and Southern African plateaus and ends in the Okavango Makgadikgadi Zambezi Basin. This basin hosts the Okavango Graben and the Eiseb Graben, considered as the terminus of the Southwestern Branch of the rift. To the southeast, the Makgadikgadi Basin is affected by a series of normal faults forming the Makgadikgadi Rift Zone (MRZ) which regional geodynamic significance remains unclear. Based on fieldwork and geomorphic analysis, we revisited the geomorphological features associated with paleolakes and the fault pattern within the Makgadikgadi Basin to better constrain the dynamics of the MRZ. Fault scarps and offsets along linear dunes show normal‐dip kinematics of faults, indicating a NW‐SE extension direction in the area. Furthermore, lacustrine shorelines in the basin are undeformed, proving that they post‐date the fault activity. The previously published ages of these shorelines demonstrate that the MRZ currently has a low tectonic activity. Integrated in the geodynamic framework of the region, these results suggest that present‐day deformation shifts toward the Okavango Graben north of the MRZ. We therefore propose a “zip‐opening” model to explain the propagation of the Southwestern Branch of the East African Rift System where the tip of the system progressively progresses southwestward, driven by motions of the continental plates.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Geological and Geomorphological Settingsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Gaudaré,

Dauteuil,

Jolivet

2024

Tectonics

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“…Although, the area experiences, low-magnitude seismicity, one large shallow earthquake occurred on the Calibration of the local magnitude scale (M l ) for Central Southern Africa 3 rd of April 2017 with a magnitude M6.5 (Asefa and Ayele, 2021;Gardonio et al, 2018;Midzi et al, 2018). This earthquake was followed by aftershocks which lasted for several months (Mulabisana et al, 2021;Olebetse et al, 2020;Midzi et al, 2018). Monitoring of earthquakes in this area is carried out by the Botswana Geoscience Institute (BGI, formally the Botswana Geological Data that is recorded from these stations is transmitted in real time to the Calibration of the local magnitude scale (M l ) for Central Southern Africa 5 BGI for analysis.…”

Section: Introductionmentioning

confidence: 99%

Calibration of the local magnitude scale (Ml) for Central Southern Africa

Shumba¹,

Midzi

Manzunzu

et al. 2023

J Seismol

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The Central Southern Africa is an area of moderate seismic activity generally caused by the presence of the East Africa Rift System. To improve the quantification of seismicity in this region, we propose a local magnitude scale (Ml), based on the original Richter definition to be used by the Zimbabwe and Botswana national networks. The magnitude scale is developed using 854 seismic events that occurred between 1997 -2000 and 2013 -2018. These events were recorded by 61 broadband seismic stations located in Botswana, Zimbabwe, and South Africa. We evaluated 6128 traces of zero to peak maximum amplitude, recorded on the horizontal channel from simulated Wood-Anderson seismograms. All Calibration of the local magnitude scale (M l ) for Central Southern Africa 6128 maximum amplitude measurements were inverted simultaneously to determine the attenuation constants. The resultant Ml is defined as Ml = log 10 A + 0.80 × log 10 (R) + 0.00086 × R − 1.37 ± S in which A is ground displacement amplitude determined from instrument corrected synthetic Wood-Anderson seismograms in nanometres, R is the epicentral distance (km), and S is the station correction. Station corrections were determined for all stations during the regression analysis resulting in values ranging between -0.44 to + 0.31. The range in station corrections suggests a strong influence of local site effects on the amplitude of the seismic signal. Without station correction, the overall standard deviation of the magnitude residuals using our magnitude relation is 0.32 with a variance of 0.10, while using station corrections, the standard deviation and variance improved to 0.17 and 0.02 respectively. There is 80 % reduction in variance when our relation is used together with station corrections. A comparison of our local magnitude relation with published mblg relationships for Southern Africa shows that these two magnitude scales are almost equivalent. The Ml equation for Central Southern Africa derived in this study has good correlation with mb values reported by the ISC and NEIC and attains systematically lower magnitude values than the South African relationship.

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Relocation of 3 April 2017 Moiyabana Earthquake in Botswana Using Seismological Data from Local Network of Autonomously Recording Seismographs and International Monitoring System Stations

Simon,

King,

Moffat

et al. 2024

Pure Appl. Geophys.

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On the 3rd April 2017 a widely felt Moiyabana earthquake shook Botswana and the rest of southern Africa. Previous Moiyabana earthquake locations used mainly teleseismic or regional seismograms; and/or non-seismic methods which include Synthetic Aperture Radar (InSAR), and magnetotelluric (MT). These results did not agree, as evidenced by the depth of the earthquake that ranged from zero to 30 km (i.e. indicating either a man-made event or a natural event); thus motivating us to re-assess the location parameters. Unfiltered seismic waveform data from the recent project of the Network of Autonomously Recording Seismographs (NARS) in Botswana was complimented with stations from the International Monitoring System (IMS) to relocate the event. Relocated parameters are origin time, epicentre, focal depth, and magnitude. Geotool software from the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), and the Regional Seismic Travel Time model (RSTT) were used to process vertical components waveforms from 9 NARS and 32 IMS stations. Geotool results are: earthquake epicentre (22.645 °S: 25.220 °E); origin time of 17:40:16.9 (UTC); hypocentral depth range of 22 to 24 km; body magnitude (mb) and local magnitude (ml) of 6.3 ± 0.6 and 6.0 ± 0.8, respectively. RSTT results are: earthquake epicentre (22.667 °S: 25.257 °E); origin time of 17:40:16.95 (UTC); hypocentral depth of 25 km; and mb of 6.65 ± 0.03. The seismological location parameters from Geotool and RSTT, agree very well within experimental uncertainties with the non-seismic geophysical methods.

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Seismotectonic analysis of the 2017 moiyabana earthquake (MW 6.5; Botswana), insights from field investigations, aftershock and InSAR studies

Cited by 6 publications

References 63 publications

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Calibration of the local magnitude scale (Ml) for Central Southern Africa

Relocation of 3 April 2017 Moiyabana Earthquake in Botswana Using Seismological Data from Local Network of Autonomously Recording Seismographs and International Monitoring System Stations

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