Abstract

On March 19th, 2005 a moderate (M~4.6) earthquake struck Monatélé, a small city near Yaoundé, the capital of Cameroon. It was the largest earthquake recorded in the area. No injuries to people or damage to property were reported. We analyse broadband seismograms recorded by the Cameroon regional network to relocate the event and determine the source mechanism. Seismicity is further correlated with the gravity data to investigate the seismotectonic implications. The epicentre lies close to the northeast segment of the Sanaga Fault, the most continuous tectonic lineament in Central Africa. The focal depth is 11 km, placing the earthquake source in the upper crust. The source mechanism was found to be dextral strike slip, with one nodal plane coinciding with southwest-northeast strike of the Sanaga Fault. The results from earthquake source mechanism, geological observations, seismicity and gravity analyses all indicate movement between the northern edge of the Congo Craton and the southern edge of the Pan-African Belt. The Monatélé earthquake therefore provides evidence that the contact between of the Congo Craton and the Pan-African Belt (the location of Cameroon’s greatest earthquake, M~5.9 in 1945) is still seismically active.

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