Deep Rupture Process of the 3rd of April, 2017 Earthquake in Stable Continental Region, Botswana

Abstract

On April 3, 2017; an earthquake of magnitude Mw 6.5 has occurred in Botswana in a region where there were no 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 a reliable source parameter for the Mw 6.5 earthquake using moment tensor inversion both in time and frequency domains from broadband waveform data. We obtained the hypocentral depth value which is of 38.4 km, deeper than the previous results. The estimated hypocentral depth of this study is approximately estimated at the boundary between lower crust and Moho depth beneath the region, reflecting a deep source that is relatively rare in stable continental regions. The result may suggest that the continental-rift initiation between weak upper mantle and weak lower crust or due to a reactivation of the pre-existing faults at deep region. The resulted focal mechanism of the event shows normal faulting with NE–SW extension. The results of this study will provide useful information about the future seismicity in this region, a stable area where rare large magnitude and relatively deep earthquakes occur.