Earthquakes in Portugal

Portugal lies near the diffuse boundary between the African (Nubian) and Eurasian plates, which runs across the Atlantic along the Azores-Gibraltar fracture zone toward the Gulf of Cadiz. Although the two plates converge only slowly, the offshore faults southwest of the mainland are capable of storing enough strain to produce very large, tsunami-generating earthquakes. The Azores archipelago, sitting on a volcanic triple junction, adds a much more frequent source of shallow seismic activity.

The 1755 Lisbon earthquake, estimated at magnitude 8.5 or greater, struck on All Saints' Day and, combined with the tsunami and fires that followed, destroyed much of the capital and killed tens of thousands. Its scale profoundly influenced European thought and is often credited with helping to found the modern science of seismology and earthquake-resistant construction.