Abstract
West Africa continues to host a growing number of low and
intermediate-magnitude earth-
quakes (M2-5) along its passive margins, and its continental interior.
Earthquake activity
in these regions raises the need to comprehend the causes and the
tectonic controls of the
seismicity. Unfortunately, such studies are rare. Here, we apply
single-station inversion
techniques to constrain fourteen focal mechanisms, computed after
compiling a set of high-
quality waveforms. We describe the connection between seismicity, the
contemporary stress
field, anthropogenic activity, and Holocene fault scarps in the region.
Our results indicate
transpressive stresses acting on the inherited brittle structures in the
passive margins. We
also observe a compressive regime in the intracontinental failed rifts.
We attribute the
seismicity to the reactivation of ‘weak’ faults in the Neoproterozoic
and Mesozoic failed rifts,
the passive transform structures, and the intracratonic Precambrian
brittle shear zones.