An offshore earthquake of magnitude 9, followed by a tsunami destroyed Lisbon, Portugal. The combination of the earthquake and the tsunami, especially with little understanding of the nature of tsunamis, caused almost universal destruction in Lisbon.
On November 1, 1755, an earthquake of magnitude 9 hit Lisbon. Houses and shops in the lower part of the city, which had been built on unconsolidated ground, were completely wiped out and most of the parish churches were also destroyed. The shock of the day on which this happened was as strong as the event itself. November 1 is All Saints Day, a sacred occasion in a Catholic country like Portugal. In such a religious place the middle of the eighteenth century there were deeply held convictions about all the earth being an orderly creation guided by its Creator for the benefit of humanity. How could such a tragedy occur on All Saints Day and how could it happen when most people were in churches and where so many of them lost their lives? There was a sense of bewilderment all around. Those who were able to get out of buildings before they collapsed ran down toward the open areas near the sea, tragically unaware that a powerful tsunami was about to overwhelm the very area they thought was safe.
The city of Lisbon is a short distance inland from the Atlantic coast on the northern bank of the River Tagus. As people moved toward the mouth of the river close to the coast they noticed that the water’s edge had moved away from the land, leaving a broad stretch of beach covered with all kinds of sea life. What they were unaware of is that the withdrawal of water from beaches is frequently the first action of tsunamis as they reach shore. There is a pause as tsunamis encounter shallow water and friction is experienced by one part of the advancing wave. The wave stalls, then, like a suction pump, it withdraws all the water in front of it and recedes back out to sea, only to return later with much greater strength. There was no understanding of tsunamis 250 years ago so no one was prepared for the wall of water that subsequently crashed on to the shore destroying everything in its path. The wave was forty feet high at first and increased in height as it made its way up the valley of the River Tagus.
The epicenter of the earthquake was located at sea about seventy miles southwest of Lisbon in a location where two tectonic plates meet, the Azores Plate and the Gibraltar Plate. Historically, those have frequently given rise to tsunamis, particularly if the quake’s magnitude is greater than 9. Thus, the result of the earthquake was first of all huge damage to Lisbon, but then lesser destruction up and down the coast as far south as North Africa and northwards to Britain and even Scandinavia. Along the French coast lakes and sea inlets were flooded. There were several phases to the tsunami. It was not just one wave that came in but rather a sequence over a period of time, so places continued to be hit at a distance over time. Lisbon was a city of 275,000 people in 1755 and first reports told of 20,000 buildings having been destroyed but this was just the beginning of troubles. As has so often happened in earthquakes fires break out and quite soon they are out of control. This was the case in Lisbon and the same thing happened more recently in San Francisco’s earthquake of 1906 and Tokyo’s of 1923.
Fires always get out of control very quickly after earthquakes for similar reasons, because they originate in numerous places at the same time. In Lisbon, candles in churches were knocked over and open fires in kitchens were also tipped over. Wood, cloth, and paper, all highly flammable materials, were everywhere available to assist any flame. To make matters worse, strong northeasterly winds sprang up around the city. Fires blazed on for a week, destroying all that was left standing from the destruction cause by the earthquake. All kinds of valuable collections of silks, spices, and goods were destroyed by the fire, as were some outstanding buildings such as the Opera House, just built in the year of the earthquake, and the Patriarchal Church and Royal Palace. The major libraries of the city lost more than 70,000 volumes. Of special interest to those who disliked the authoritarian rule of the church was the news that one of the buildings destroyed was the headquarters of the Inquisition, the branch of the church that was responsible for the persecution and torture of all who opposed the beliefs of the church.
At least 30,000 people lost their lives in the city of Lisbon and a general state of chaos followed the tsunamis and the fires that followed. The sad situation that emerged was an opportunity for scavengers and thieves. They began to search all over the ruins of the city, among the living as well as the dead, to find what they could. Their behavior, added to all the destruction, gave rise to what can only be described as mass hysteria among survivors. The need for some form of authority coupled with effective control over crime became urgent. The government of Portugal had collapsed as a result of the widespread destruction and there was no obvious source that could exercise control. The king decided to appoint one man, on a temporary basis, to take complete charge of all the affairs of the city. He was given absolute authority. He had to launch quickly into three immediate tasks: establish order, fight the fires, and bury the dead. To make it clear to all who might try to steal or profit from the high demand for food, this man arranged to have several gallows erected in the city. The bodies of more than thirty looters were soon found on these gallows, left there for the public to see.
Securing the approval of the church to bury the dead quickly was a difficult task, despite his authority. Where you were buried was seen to be as important as how you had lived because it affected your fortunes in the afterlife. Burial in a consecrated plot beside the church was essential because that would mean your beliefs and behavior had been approved by the church. Without that approval you were certainly destined for hell. However, there were neither enough priests nor sufficient time to arrange for each burial and the man in charge wanted to conduct a mass burial at sea to prevent the spread of disease. Bodies had already been ignored for some days. The greater good prevailed and all bodies were buried at sea. The next task was to arrange temporary housing for the homeless along with public kitchens and food distribution centers. Both Portuguese and foreign ships that happened to be in the harbor were ordered to unload their provisions and sell them at reduced prices.
One foreigner visiting Lisbon who happened to be on the fringes of the city in a place that was largely untouched by the earthquake decided to record his observations of the event. It was probably all he could do because everywhere around him there was a situation of panic. He noted a slight tremor in the ground around 9:30 in the morning and thought it must be the result of a passing wagon. The tremor lasted for about two minutes and was followed, after a short pause, by a violent shaking that made nearby houses split and crack. This much stronger shaking went on for what he felt was about ten minutes and was accompanied by a steady build up of dust in the air, latterly so heavy and dark there was no daylight. Suddenly, he noted, the dust settled down and the sun appeared. There was a short period of nothing happening before he felt a third and far greater shaking. He could see at a distance building after building collapsing. Once again the sun was obscured and he began to hear the cries of pain from all directions. Soon afterward he saw fires springing up here and there and he could see people running away from them. A wind had sprung up and no one was trying to cope with the flames. Every person was trying to save his or her own life. Fortunately, this foreigner’s written record was preserved and later added to the official documentation.
About an eighth of the 275,000 people of Lisbon had perished along with its buildings. The fires raged on for five days and Lisbon, one of the largest cities in Europe, famed for its architecture, was reduced to ashes. Architectural treasures from the days of Moorish occupation were lost. The city’s opera house, built earlier in the same year as the earthquake, had gone. The cathedral and all the major churches were ruined and the Royal Palace was no longer habitable. The city’s hospital was overtaken by fire and its destruction added significantly to the total loss of life. The total value of property losses was estimated to be $100 million. This earthquake was the first in all history to be subjected to very close scientific investigation. The same man who had been given absolute authority to bring order and provisions after the earthquake arranged for a questionnaire to be sent to every parish in all of Portugal asking them for all the information they could provide as to the time and duration of the shocks and aftershocks, how high the sea waves came, and how many people had been killed. This record was kept in Portugal’s national archives and it has been a very valuable source of information for succeeding generations on the whole subject of earthquakes and their effects. Also included in this record were the notes from the foreign observer.
The work of restoration began quickly. Debris was cleared from the city within a year and by the end of that year the various branches of government were in place. Fortunately, the new prime minister decided to take account of the information that had been collected from all the areas affected by the earthquake and use it as a guide in the design of what would be a new city. There were many aspects of the old city that both contributed to earthquake destruction and hindered escape when tragedy struck. The new prime minister was determined to correct these weaknesses of design and, as a result of the work he did, he became known in history as the father of seismology. One improvement he introduced seems very simple to us today but was revolutionary in 1755. It was to make streets wider and remove curves. This one change would enable people to escape quickly from a collapsed building without having to cope with the debris that so often filled the older streets. In addition, fires could not jump easily from one side of a street to the other so they would not get out of control as quickly as they formerly had. Even in modern times, as was seen in Japan in the aftermath of the 1923 earthquake, a simple idea like this is not always implemented. Instead, in Japan, streets were left in the older narrow format.
To ensure against the collapse of buildings in an earthquake, the new prime minister did several things. First, he arranged to have models of buildings drawn to scale and then arranged for army units to parade backwards and forwards with their horses around the models to find out if their weights and activities affected the models in any way. As the design of new buildings progressed he finally settled on a new kind of structure consisting of a flexible wooden skeleton around which masonry walls would be built. The idea was that the flexible skeleton would be firmly anchored in order to hold the masonry walls in place during an earthquake. At the same time, the masonry would protect the wood from catching fire. This was perhaps the first occasion when a building design was carefully related to the effects of the earthquake. It may have been the first anti-earthquake building system ever designed. Such systems became fixed law for Portugal and guided Lisbon’s new city plan. There were two other valuable initiatives that the prime minister added: he included the details about earthquake experience that had been collected and made them part of the overall plan for the city and added, in some detail, all that was known about the behavior of animals before and during earthquakes. Today we are well aware of the warning signals we get from all forms of life with regard to earthquakes but this was probably the first time they were given serious consideration.