资源环境科技发展态势分析平台

On 3 April 2017, a M-w 6.5 earthquake struck Moiyabana, Botswana, nucleating at >20km focal depth within the Paleoproterozoic Limpopo-Shashe orogenic belt separating the Archean Zimbabwe and Kaapvaal Cratons. We investigate the lithospheric structures associated with this earthquake using high-resolution aeromagnetic and gravity data integrated with Differential Interferometric Synthetic Aperture Radar (DInSAR) analysis. Here we present the first results that provide insights into the tectonic framework of the earthquake. The ruptured fault trace delineated by DInSAR aligns with a distinct NW striking and NE dipping magnetic lineament within the Precambrian basement. The fault plane solution and numerical modeling indicate that the cause of the earthquake was 1.8m displacement along a NW striking and NE dipping normal fault, rupturing at 21-24km depth. We suggest that this seismic event was due to extensional reactivation of a crustal-scale Precambrian thrust splay within the Limpopo-Shashe orogenic belt.

Plain Language Summary Most earthquakes occur along plate boundaries. However, on 3 April 2017, a M-w 6.5 earthquake rocked Moiyabana, Botswana, within the stable continental interior similar to 300km away from the nearest zone of active tectonics. This earthquake occurred in a region where there is no surface expression of faults and where the last major tectonic event occurred similar to 2Ga. We used high-resolution aeromagnetic and gravity data integrated with Differential Interferometric Synthetic Aperture Radar (DInSAR) analysis to investigate the fault that ruptured. We present the first results that show that the ruptured fault trace delineated by DInSAR aligns with a distinct NW striking and NE dipping magnetic lineament within the Precambrian basement. Our results further suggest that the cause of the earthquake was similar to 1.8m displacement along a NW striking and NE dipping normal fault that ruptured at similar to 21-24km depth. This seismic event was due to extensional reactivation of a crustal-scale Precambrian thrust splay within the Limpopo-Shashe orogenic belt that resulted from the collision of the Kaapvaal and Zimbabwe Cratons.

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