How a ruined kingdom sparked seismology
On the 1st of November 1755 at approximately 9.30am one of the most devastating earthquakes in Europe’s history struck the prosperous seaport of Lisbon, Portugal. It is estimated the earthquake was between 8.5 and 9 on the Richter scale.
The terrifying shaking lasted between 4 and 6 minutes opening 5 meter wide fissures in the ground throughout the city. Another major shock arrived, 10 minutes later, followed by a third weaker shock.
The earthquake struck on All Saints Day, a Christian festival. Dozens of Lisbon’s beautiful stone churches, museums and palaces, none of which was designed to cope with earthquakes, collapsed. Over 85% of the city was reduced to ruins.
The sea receded from the port area; 40 minutes after the main earthquake a 12 metre tsunami surged in, killing thousands of people. Fires engulfed the city for five days killing thousands more people. It is estimated that one third of Lisbon’s 275,000 people were killed.
The King of Portugal, Joseph I, survived but was so traumatized he refused to live within the walls of a building, so he set up the entire court in a tented city located on the outskirts of Lisbon. The court remained there, in tents, until the king died 22 years later.
Prior to the earthquake, Portugal was in the grip of the Inquisition. The Inquisition’s job was to search for those who had converted from Judaism to Catholicism but were suspected of secretly continuing to practise Judaism. Death, usually involving being burned alive, was the penalty.
The Grand Inquisitor and enthusiastic enforcer was a Jesuit priest called Gabriel Malagrida – he viewed the earthquake on All Saints Day as a sign of God’s wrath for Lisbon’s sins. This was in marked contrast to the Enlightenment, a revolutionary intellectual and philosophical movement taking hold in Europe at the time.
The Enlightenment questioned the roles of religion, the state and the aristocracy in the lives of citizens. It advocated tolerance, liberty and the separation of church and state. One of its foremost figures was FrancoiseMarie Arouet aka Voltaire.
On hearing of the earthquake, he questioned the existence of a benign God if such death and destruction could be brought to bear on the god-fearing community that was Lisbon.
Immediately after the earthquake, King Joseph I appointed his very capable prime minister, Sebastian Jose Carvalho e Melo to supervise the reconstruction of the city.
Carvalho despised the Grand Inquisitor and had no time for the sense of entitlement of the corrupt Portuguese aristocracy. Luckily for Carvalho the aristocracy hated the King, so he had a trusted ally in the King.
Carvalho appointed a brilliant engineer, Manuel da Maia to design a new city. Da Maia standardised construction so that houses could be built quickly but in this process he was mindful of how buildings and the layout of streets had been affected by the earthquake and how fatalities could be mitigated in the future by good design.
This marked the first time in Europe anyone had considered earthquake engineering.
Meanwhile da Maia’s boss, Carvalho searched for a natural source of earthquakes.
He organised the distribution of a questionnaire to be completed by the priests in each of the parishes in Lisbon. It asked questions such as, what time and from which direction did the quake strike and how long did the shaking last?
Some of these records survive to this day and amount to the emergence of the science of seismology although, mistakenly, Carvalho thought the source might be subterranean gas explosions.
Alas Sebastian Carvalho was no saint. There was an attempt to assassinate the King and on highly questionable evidence, Carvalho succeeded in convicting the hated Grand Inquisitor, Gabriel Malagrida. He had Malagrida publicly strangled at the garrotte a handheld wire, in Lisbon’s Rossi Square.
The 1755 Lisbon earthquake was a disaster that contributed to a major rethink in politics, philosophy and science and was a key milestone on the road to a more liberal, democratic and enlightened Europe.