Source parameters of the moderate Mozambique – Zimbabwe border earthquake on 22 December 2018

Abstract

An earthquake of moment magnitude (Mw = 5.6) occurred in central Mozambique close to the Zimbabwean border on 22 December 2018 at 05:37:4 GMT. The event was widely felt in Mozambique, Zimbabwe and some parts of South Africa. Buildings were damaged near the epicentre but without loss of human life. An intensity survey was conducted by manually distributing questionnaires in the affected areas as well as from online submitted questionnaires, giving a total of 215 replies. We obtained the highest intensity of between VII and VIII in Espungabera, a town approximately 25 km from the epicentre, and in Chipinge about 50 km from the epicentre. A source depth of 21.2 ± 3.8 km in the lower crust was obtained. The moment release, measured from S-wave spectra, was 3.16 × 1017 Nm yielding a moment magnitude (Mw) of 5.6. Stress drop and source radius of the mainshock were estimated to be 11.7 ± 2.3 MPa and 2.3 ± 0.3 km respectively. The focal mechanism of the event shows normal faulting with nodal planes oriented in NNE-SSW direction. The first nodal plane was at a strike of 209°, dip of 54°, and had a rake of −78°. The second nodal plane was at a strike of 9°, dip of 38° with a rake of −106°. These results are consistent with most fault plane solutions previously obtained for earthquakes in Central Mozambique.