The tiered hillsides and yacht-dotted coastline of Lisbon, Portugal seem much more at home in our holiday daydreams than rousing debate over reinforced concrete walls and steel structures. But, unlikely though it may outwardly appear, this sunny city is also the birthplace of seismology and earthquake engineering due to the effects of a catastrophic quake in the 18th century.

 

It’s an event that is not often talked about, but one which shaped culture and philosophy in Europe.

 

Mid-morning, on All Saints’ Day in 1755, as families gathered to remember loved ones in church, a (estimated) magnitude 8.5-9.0 struck in the Atlantic Ocean, about 200km from the southwestern corner of Portugal. It shook Lisbon for between three and six minutes, destroying 85% of buildings in the area and ripping five metre-wide chasms in the streets.

 

Many who survived the falling buildings found solace in the open space of the seaside docks. They witnessed the tide pull out – revealing a seabed full of shipwrecks and long lost cargo – only for it to rush back in again as a tsunami, pooling the town with three substantial waves. In fact, Lisbon’s shake triggered tsunami around Europe and the regions connected by its oceans – with notable damage in Finland, Ireland, and a 20 metre high wave in North Africa.

 

To further add to the city’ woes, fire broke out and ravaged the ruins for five solid days.

 

In total, of the city’s 200,000 population at the time, 40,000 were killed – making the 1755 Lisbon Earthquake one of the most devastating in world history.

 

The aftermath, too, was a fairly coarse affair. The army forced citizens to remain within the city’s walls, lifting dead bodies and clearing debris. Thirty people were publicly executed for looting crimes and by all accounts there was the savage, dusty squalour of hard labour.

 

Despite these grim realities, the streets were cleaned up within one year and the new city plan began rolling out at great pace – quite in contrast to the drawn-out, but democratic process the developed world now follows when rebuilding after earthquakes.

 

 

Staunchly Roman Catholic, the people and philosophers of Lisbon believed God’s wrath was undoubtedly the cause. They were confused and frightened. How could He, who they have looked up to and sought support from – destroy all that they had, including almost every church in the region? And why would He strike on an important religious holiday when families were together and feeling relaxed?

 

Philosophers, naturalists and theologians argued intensely about the cause, and for the first time scientific theories were discussed openly and promoted to the public throughout the continent. What followed changed the perspective and belief systems of Europeans forever, and several individuals stood out as pioneers in the study of seismology.

 

Immanuel Kant was a young man at the time, He collected all that he could to build a more rational theory of how the disaster occurred. Rather than punishment from God, Immanuelhypothesised that it was to do with the movement of ‘subterranean caverns filled with hot gases’ - not entirely correct as we know it today, but certainly one of the first attempts at scientific geology which has developed over the centuries into our current understanding of earthquakes and their causes.

 

Another who demonstrated an interesting scientific perspective was the polarising Prime Minister, Sebastião de Melo, son of a country squire – loved by the King but despised by the Aristocrats – who brought practicalities to the rebuild process and also enacted a qualitative study into the earthquake’s affects.

 

He sent a survey to every church unit operating in the area and asked questions like:

 

  • At what time did the earthquake begin, and how long did the earthquake last?
  • Did you perceive the shock to be greater from one direction than another? Eg: from north to south? Did buildings seem to fall more to one side than the other?

  • Did the sea rise or fall first, and how many hands did it rise above normal?

 

The priests’ answers have helped modern scientists greatly in piecing together the events of that day, the causes and how improvements can be made to keep buildings standing and limit fatalies for future 8.5+ magnitude shakes.

 

The priests’ answers to Prime Minister Melo’s questionnaire are still available for you to view today – archived away in the Torre do Tumbo national archive building right in the heart of the city.

 

Our approach to seismic events today owes much to this city's tragic past.

 

 

 

 


   

 

 

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