Seismotectonics of Portugal and its adjacent Atlantic area

A study of focal mechanisms of earthquakes and stress indicators are presented for Portugal and its adjacent Atlantic margins. Recently Riberio et al. (1996) published a work on this subject. In this study, we introduce new focal mechanisms of nine earthquakes. We use these results together with 12 other focal mechanisms and the main tectonic features in the region to define more accurately the type of mechanism and the stress pattern of the region. All the focal mechanisms used in this study differ partially but are compatible with the regional stress held. The stress indicators resulting from focal mechanisms and other geological and geophysical data show that the Portugal continental and its Atlantic margins are under horizontal pressure in NNW-SSE direction, with a greater proportion of strike-slip and reverse-oblique mechanisms for the whole area. (C) 2001 Elsevier Science B.V. All rights reserved.