Seismotectonic analysis of the Anker area, Kunene region north-western Namibia

Abstract

Recently, a swarm of seismic events occurred within the Kunene region (NW of Namibia) with magnitude values going up to ML 4.6. Some of the events alarmed the Anker community and have become of national interest. In order to understand the source of this seismic activity, the Geological Survey of Namibia (GSN) and the Council for Geoscience (CGS) of South Africa installed a temporary network of 10 seismic stations in the Anker area to monitor seismicity for a period of 3 months from 20 June to 24 September 2018. More than 1600 microseismic events were recorded and located within the boundaries of the array, which was roughly 50 km × 50 km. The stations were installed in a 50 km × 50 km radius to have an accurate overlap of the network coverage and also by the spatial distribution of the known seismicity in the study area. The magnitude of the events ranged from ML − 1.1 to 3.6 and occurred at depths of less than 20 km. To improve the location of earthquakes, a new velocity model was developed using high-quality seismic dataset recorded by the temporary network. The seismic data was used to determine a minimum 1-D velocity model, which was used for the relocation of the earthquakes using the double difference method. The relocated solutions provided information to explain the seismotectonics of the region and establish the source of the current seismic swarm. Lineaments were mapped using magnetic data to identify the sources of the seismicity. Focal mechanism analysis of some of the events indicates the area is highly faulted with predominantly normal faulting.