This paper reports the preliminary results of a geological survey performed to study the tectonics of Povoação and Nordeste Volcanic Complexes at S. Miguel Island. The main systems of faults and dykes trend WNW-ESE to NW-SE with the principal faults presenting normal and left lateral strike-slip components. Some WNW-ESE to NW-SE structures show either left or right lateral strike-slip component, that may be related with a stress field change in time. At Nordeste a second set of faults, trending WSW-ENE to SW-NE, was mapped. The spatial and temporal relations between these fracture systems are under investigation.​