Portugal, though known as a moderate seismic hazard country, is, yet, susceptible to significant occurrences, as evidenced by the regularity of its historical record.
The Lisbon region and the Algarve Region are located in the highest seismic hazard area. To refer are also the regions of Tagus Lezíria and Setúbal Peninsula, located in the ‘Fault of Tagus Lower Valley’, that also present a high seismic vulnerability. The volcanic activity of the Azores archipelago and its particular geographical location turn these islands into one of the most vulnerable contexts, regarding seismic hazard impact. The Coastal Alentejo region, presents a medium-high impact index, along with a significant frequency of occurrences. Finally, the Central Alentejo is depicted as a region of medium/ low impact index, with the particularity of presenting an intense regularity of occurrences.
| Year | Intensity / Mercalli Scale (MCS) |
|---|---|
| 1531 | IX |
| 1755 | IX |
| 1858 | IX |
| 1909 | V |
| 1969 | VIII |
Major earthquakes in the Portuguese mainland
| Year | Area | Intensity / Escala de Mercalli (MCS) |
|---|---|---|
| 1522 | S. Miguel | X |
| 1547 | Terceira | VII-VIII |
| 1614 | Terceira | IX |
| 1757 | S. Jorge/ Pico | X |
| 1800 | Terceira | VII-VIII |
| 1801 | Terceira | VIII |
| 1841 | Terceira | IX |
| 1852 | S. Miguel | VIII |
| 1973 | Pico/Faial | VII-VIII |
| 1980 | Terceira/ S. Jorge / Graciosa | VIII-IX |
| 1998 | S. Jorge/ Pico/ Faial | VIII-IX |
Major earthquakes in the Azores Island
Major mainland faults
Macro seismic intensity in Portugal