Source parameter inversion of a reservoir‐induced seismic sequence: Lake Kariba, Africa (1963 September)

Abstract

The depth and seismic source parameters of the three largest reservoir‐induced earthquakes associated with the impoundment of Lake Kariba, Africa, were determined, using a moment tensor formalism of the generalized inverse technique. The events, characterized by mb > 5.5, consisted of the foreshock and main event (0640 and 0901 GMT, 1963 September 23) and the principal aftershock (0703 GMT, 1963 September 25). From the analysis of analogue rift valley source crustal models, a three‐layer over a half‐space model were selected for the analysis of the Lake Kariba events. The epicentral proximity and the comparable source parameters of the three large events suggest a common source fault with an approximate strike of S 9°W ± 4°, dip of 62°± 10°, and rake of 266°± 4°. The body wave modelling indicates that the Lake Kariba events occurred at depths of less than 10 km. The inferred source parameters, complemented by the structural maps derived from the photo‐interpretation of Landsat imagery of the region, indicate a normal fault that uniquely transects the reservoir's deep Sanyati Basin in a north‐south heading. The active fault seems to correlate with the location of the Umi River's submerged river channel. The confirmation of shallow depths and the determination of source parameters establishes a basis for addressing the actual triggering mechanisms of these earthquakes. Copyright © 1983, Wiley Blackwell. All rights reserved

Publication Title

Geophysical Journal of the Royal Astronomical Society

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