ISDR Informs - The Americas

The Lisbon earthquake of November 1, 1755: The first “modern” disaster?

At 9:40 a.m on November 1, 1755, All Saints Day, Lisbon, Portugal was struck by an earthquake that nearly destroyed the entire city. The seism was felt in all of Western in Europe kiillngan estimated 60,000 to 100,000 people. The epicenter was located in the Atlantic Ocean, some 200 km southwest of Cape Saint Vincent, and its magnitude was calculated at approximately 9 on the Richter scale. The event was followed by a tsunami and fires that further devastated the city.

This seism is regarded by some researchers as the “first modern disaster,” since it was the first catastrophe that led to the first coordinated response during search and rescue activities, as well as planned reconstruction and reinstatement efforts including measures to mitigate the destructive effects of future earthquakes. In addition, some researchers believe that the earthquake was the first event that leadingn to the development of modern seismology.

It is important to remember that the earthquake took place during the Age of Enlightenment, and it unsettled the trends of thoughts of intellectuals in that period. In 1747, Dennis Diderot, a famous French revolutionary philosopher, became the chief editor of the L’Encyclopédie (The Encyclopedia), and between 1751 and 1772 he published 28 volumes as a result of collaborative efforts with more than 100 intellectuals. Although the main interest of the encyclopedists focused on scientific and technological aspects, the Encyclopedia became the niche of the so-called social philosophy —theories related to social organizations, human nature, economics, politics and governance.

The Marquis of Pombal

During the activities following the earthquake, the actions of Sabastiao José de Carvalho e Melo, better known as the Marquis of Pombal, stood out. Acting as the Prime Minister of King Joseph of Portugal, he personally led the search and rescue efforts, and designed and implemented a reconstruction and reinstatement plan.

The beginning of the reconstruction activities overlapped with the reinstatement phase. Engineers and architects who worked with Pombal developed a grid design on a north-south axis in the Baixa neighborhood, which is close to the Tajo River. Unfortunately, Pombal’s project was not continued by his successors. When the royal family fled to Brazil during Napoleon’s invasion, Rio de Janeiro became the capital of the Portuguese empire, leading to Lisbon’s decline of power in the empire.

Pombal not only carried out reconstruction activities. He also actively sought information in an effort to better understand the chain of events leading up to the earthquake. In fact, he sent a questionnaire to all the parishes with the following questions:
How long did the earthquake? How many aftershocks were there? What type of damage last was caused? Was there any unusual animal behavior preceding the event? (Pombal was far ahead to modern Chinese studies of the 1960s), What happened in the water wells?

Many of the questions that the Marquis of Pombal asked in 1755 are still used today in questionnaires applied in the aftermath of a disaster to develop isoseismic maps (seismic intensity). Without this type of information, it would have been very difficult for modern scientists to understand the Great Lisbon Earthquake.

The Lisbon earthquake profoundly marked the European trends of thought at that time. It was heatedly discussed, perhaps for the first time, if maybe the earthquake had occurred due to natural causes, rather than divine wrath .The Church interpreted the earthquake as an act of God and announced that in the future there would be greater catastrophes as punishment of Goad. Thus, a controversy began which still persists to this day.

Voltaire and Rousseau

These important thinkers of the eighteen century held an interesting epistolary debate around the meaning of the earthquake and its natural or divine origin. The following quote is from a letter sent from Rousseau to Voltaire, dated August 18, 1756. The paragraph is relevant to the modern concept of mitigation of disasters resulting from seismic events.

Without leaving your Lisbon subject, concede, for example, that it was hardly nature that brought together twenty-thousand houses of six or seven stories (in Lisbon). If the residents of this large city had been more evenly dispersed and less densely housed, the losses would have been fewer or perhaps none at all.”

Regarding the behavior of the population as a result of the earthquake, Rousseau asks, “How many unfortunates perished in this disaster through the desire to fetch their clothing, papers, or money?

Final considerations

The Lisbon earthquake was the first disaster of natural origen for which a State accepted its responsibilities of search and rescue, as well as regarding the design and implementation of a reconstruction program. It also generated an opinion contrary to the supernatural origin of disasters in general and seismic events in particular.

The Marquis of Pombal was the first person in history to foster a scientific and objective description of the causes and consequences of an earthquake. For this reason, some consider him the predecessor of modern seismologists.

For his part, the philosopher Jean Jacques Rousseau had a futuristic vision of what we would now call “seismic micro-zoning” based on his comments on the overcrowded buildings in Lisbon and his viewpoint, also ahead of his time, on the need to prepare the population to cope with effects of seismic events.

Juan Murria
Director, Risk Research Center, University of Falcón, CIR UDEFA
Advisor, Venezuelan Foundation for Seismic Research, FUNVISIS
Vice-president for Latin America, GADR.
(58-212) 977-0233,

The author has worked on the issue of historic seismology as a tool for preserving the historic heritage built in seismic regions. This is related to the risk management of culture heritage, included in the Hyogo Framework for Action, section 3.3.

This article is the result of long and interesting conversations with Professor Rusel Dones who, jointly with Professor Hérnico L. Quarantelli, founded the Disaster Research Center housed at the University of Delaware.

Professor Dynes has written a number of comprehensive documents about the 1755 Lisbon earthquake, also known as the Great Lisbon Earthquake. This article is also based on his research papers.

1 A way to represent graphically the intensity levels of an earthquake shock is through isoseismic maps, which include curves that connect points with equal intensity levels of a particular event. These maps use the Mercalli Modified Scale.