In the last third six years various research works have been produced to study the earthquake mecha- nism of events M equal or greater than 6, in order to characterize the geodynamic complexity. In this work we summarize these studies and present their main conclusions. The analysis of focal mechanisms indicates evidences of two zones with different pat- terns of movement and rates of deformation. In zone I, between longitude 30oW and 27oW, most current situations are left strike slip with horizontal E-W compression axis and N-S traction, with deforma- tion rate of 6.7mm/yr. In zone II, between longitude 27oW and 23oW, the seismic tensor indicates a normal mechanism with horizontal NE-SW traction axis and a deformation rate of 3.1 mm/yr.