The effects of the 1755 Lisbon earthquake and tsunami on the Algarve region, southern Portugal

The 1755 Lisbon earthquake (magnitude c. 8-5Mw) killed between 15,000 and 20,000 people, of whom an estimated 1020 lived in the Algarve. The earthquake cost Portugal between c. 32 and 48% of its Gross Domestic Product, probably making it financially the greatest natural catastrophe to have affected western Europe. Using a combination of archival information and data collected in the field, this article discusses the devastating effects of the earthquake and tsunami on the economy, society and major settlements in the Algarve, and the recovery of the region in the years that followed. Today the Algarve is one of Europe's principal tourist destinations and a region vital to the Portuguese economy. The 1755 earthquake was not a one-off event and the Algarve, which now houses a resident population of over 400,000 – a figure that more than doubles with tourists in the summer months - is highly exposed to earthquakes and tsunamis. An earthquake of similar size (minimum estimated recurrence 614±105 years), is viewed as a worst-case future scenario. Although strict building codes which apply to the whole country were pioneered in Portugal following the 1755 earthquake, and have been revised on many occasions, there is a recognised need for more detailed hazard maps and emergency plans for the Algarve. These have already been produced for Lisbon and in the Algarve a start has been made, where a tsunami risk map has recently been completed for Portimāo concelho¹ (i.e. county).