The Congo Basin. (a) Earthquake focal mechanisms and centroid depths from this study. No gCMT mechanism was available for the event marked by a ?, so a mechanism consistent with available data was assumed for depth-phase modelling. Events on the EARS are shown in Figs 5 and 6. EHB catalogue earthquakes are shown as small black dots. (b) Free-air gravity anomalies over the Congo Basin, with centroids indicated by colour of points for major earthquakes. (c) Lithospheric thickness across the Congo Basin. The Congo Basin formed within the extent of the Congo craton, associated with thick lithosphere. The effects of basin formation on the lithospheric thickness are considered by Crosby et al. (2010). (d) Sediment thickness, from Laske & Masters (1997).