On December 27th, 1722, an earthquake destroyed many towns, cities and villages in the Algarve with a tsunami inundating low-lying areas of Tavira.
Scientists remain divided as to whether the epicentre was offshore to the north-west of Tavira, or offshore, close to 37°01′N, 7°49′W.
The 1722 earthquake was 33 years before the great earthquake of 1755 which remains an integral part of Portuguese history, mainly due to its effects on Lisbon which was wiped out by structural collapse, fire and then the flooding from a tsunami that raced up the Tagus.
Most of the documentation of the 1722, Algarve event was sent to Lisbon for archiving and so was lost in the fire that followed the 1755 earthquake.
But the few existing records for the 1722 earthquake describe a destructive series of events affecting several Algarve cities with earth tremors so strong that they made the bells ring out in Tavira, Faro and Loulé.
The 1722 earthquake was felt throughout the Algarve. In Tavira a caravel moored on the river Gilão was left high and dry before the tsunami hit with the dumbfounded crew able to walk to shore.
The intensity is estimated to have registered 7.8 degrees on the Richter scale which triggers general panic: collapse, destruction of serious damage to many buildings, general damage to foundations, fractures in the ground, and the formation of springs and mudslides. The later Lisbon earthquake measured at 8.7 - 9.0 on the Richter scale, not that anyone was measuring things with such accuracy back then.
The earthquake of 1722 was probably caused by a diapirism, where dense rock from deeper levels, under high pressure, has pierced shallower materials.
As a result, Loulé was all but destroyed.
Recent studies of seismic risk estimate there would be around 12,000 deaths if an earthquake equal to that of 1722 occurred now.
