1522 Vila Franca earthquake
The 1522 Vila Franca earthquake, alternately the 1522 Vila Franca landslide (Portuguese: Subversão de Vila Franca or Terramoto de Vila Franca) refers to the great earthquake and landslides that occurred between 21–22 October 1522, in the municipality of Vila Franca do Campo (then provincial capital), on the island of São Miguel, in the Portuguese archipelago of the Azores.
The earthquakes' epicentre were situated several kilometres north-northwest of Vila Franca, and had a maximum intensity of X (Very destructive) on the European macroseismic scale. This resulted in the movement of landforms above the settlement, resulting in landslides and lahar that moved 6,750,000 cubic metres (238,000,000 cu ft) of material down the surrounding slopes, causing the destruction of buildings, deaths and inundated the settlement with debris. As a consequence almost the entirety of the settlement, between 3000 and 5000 people, were killed. In addition to the destruction of Vila Franca, the earthquake affected the neighbouring settlements, including Ponta Garça, Maia and Porto Formoso (where thousands were killed). A tsunami formed by the lahar caused the destruction of several boats that were located near the islet of Vila Franca, and the death of at most a hundred people. Gaspar Frutuoso, writing 70 years following the destruction, remembered a complete record of the events, writing a oral romance on Vila Franca.
Between the end of the 15th and beginning of the 16th century, the settlement of Vila Franca do Campo became a strong provincial capital of the island of São Miguel. Elevated to the status of municipality in 1472, the town was the centre of the principal civil and religious institutions of the island, residence of the Donatary-Captain and, by consequence, the seat of the islands' most powerfal family (the Gonçalves da Câmara clan), that would later receive the title of Counts of Vila Franca. The presence of the main customshouse and relative shelter of the villages' islet, made the port of Vila Franca the primary entryway to the island.
Having never suffered an attack or been affected by calamity, Vila Franca do Campo was by 1522 a prosperous and developing centre, with over 5000 inhabitants (or approximately 25% of the island's population). Most of the population settled along the coast, between the mouths of the ravines of Ribeira da Mãe de Água and Ribeira Seca (providing potable water), while the interior (that extended into the Água de Pau Massif) was less populated, especially near the Rabaçal and Louriçal hilltops (separated by the Ribeira da Mãe de Água valley). About 600 metres (2,000 ft) from the village was the islet of Vila Franca, which was a navigating landmark and provided some shelter from southern squalls.
Owing to the lack of contemporary building materials, most of the buildings in the village were constructed from loose masonry stone, and filled with gravel or stone. Only the homes of the landed gentry and the principal facades of the better properties were plastered with clay. Yet, the lower quality clays on the island meant that these too were weaker and easily crumpled. The difficulty to produce tile locally, meant the richer nobles and religious buildings were covered in tile, while poorer homes were framed in culm and covered with hay or straw. The elevated hardness of the basalt stone, made working the material difficult, creating rounded surfaces that were fragile to masonry, that when combined with the elevated weight of the walls, resulted in constructions that were vulnerable to seismic activity.
In accordance with the Romance de Vila Franca on the calm night of 21 October 1522:
- ...//Quarter of the moon was ///It was a Wednesday //Wednesday sad day //And in a night more serene //The heaven could do did //That that could run lifted //Nothing that he felt //No breadth of wind //Nor treeleaf waved //Starring night was the heaven //Clouds did not darken
The calmness lasted little; around two in the morning, local time, as related in the Saudades da Terra (authored by Gaspar Frutuoso):
- ...with a starry night and clear, without a cloud in the sky, there was heard in all the island a grandioso and spontaneous tremor of earth, that lasted for the space of a creed, that appeared that the elements, fire, air and water, fought at the centre, making them great concussions, with snorting and horrendous movements, like raging sea waves, appearing to all inhabitants of the island that turned to center, as if the sky was falling. And finishing in the space of the Creed or Our Father and Ave Maria all or more, it began again to shake softly as much.
During that dawn and until midday on 22 October, aftershocks continued.
The great earthquake, whose epicentre was estimated at some kilometres north-northwest of the town, in the area of Monte Escuro, culminated in a scale X event, resulting in landslides throughout the island, likely influenced by a saturated sub-soil from torrential rainfalls several days earlier. The island's volcanic terrain, consisting of low-density pyroclastic materials, such as the pumice stones that comprise the flanks of the Água do Pau Massif, as susceptible to landslides resulting in the creation of lahars. Similar conditions on the northeast coast of Faialense Caldera occurred during the July 1998 earthquake.
Gaspar Frutuoso continued, noting how the great landslides were terrifying:
- ...there were no grotto, from the south to the northeast, that did not run with ravines of mud.
Of the multiple landslides verified during the events, there were also victims in other parts of the island, especially in Maia, where a gigantic avalanche of mud descended along the flanks of Monte Rabaçal, following the course of the Ribeira da Mãe de Água and later spread over the whole town. As Gaspar Frutuoso noted:
- ...the ravine to the east, where the town was, everything was devastated and the inhabitants all almost dead. Only from the same ravine to the west, escape a few houses, a majority of those fells, where remained alive only 70 people more or less, of those they began to cry greatly, calling to God and others to the Virgin Mary...'
The mud arrived at the port and fell to the sea, taking with it some of the populous and causing a tsunami that destroyed ships that were anchored in the bay. As Gaspar Frutuoso indicated:
- ...there were in the port then four or five boats sheltered in the islet for departure to Portugal, which caused the death of more people there where they gathered there to make the voyage.
A study of the resulting deposits from the 1522 landslides permitted an estimate of the material that spread across Vila Franca from the headlands of the Ribeira da Mãe d’Água in the northwest and south of the Pico da Cruz, from Monte Rabaçal. Breaking from an area along the south-southeast flank, up to 6,750,000 cubic metres (238,000,000 cu ft) of debris ran down the ravine, at a speed that was estimated at between 1–3 metres per second (3.3–9.8 ft/s), reaching the centre of the village in a few minutes and covering it completely. The dense current of material razed the remaining buildings and carried many of the Vilafranquenses unhappily to the sea. Another torrent of less magnitude, generated in the headlands of the Ribeira Seca, followed the ravine and spread across the eastern coast, in the area of the parish of Ribeira Seca.
The consequences were tragic: between 3000 and 5000 people were killed in the village, many caused by the landslides and lahars that followed the watercourses. Much of the central part of the town was covred in mud and landslide material, with the port disappearing under a layer of pumice. As Gaspar Frutuoso concluded:
- ...and in the light of day, they collected a few people that lived from the mounts and the farms, and those that remained alive in the outskirts, all scared from the great tremors and sounds that they heard; and seeing the town in the state it was found, were astounded. Many people from all the island had their homes, parents, friends and familiares, sent each to dig where they stood, some to take out their dead bodies, others to find money and implements they had in their homes, others to do the same for the bodies and belongings of their parents and familiares. And thay way they dug in many parts of the town, e some found bodies along roads and others in their homes or margins, between which they found some alive.
- ...In one tragic night many lives were ended and everything became covered, of which no noble had houses, nor high buildings, nor sumputuous temples, nor nobles or simple people throughout the morning appeared, becoming everything flat and ground, without a sign or sight of where the town had been.
The catastrophe became known as the subversion of Vila Franca or burial of Vila Franca, and marked a profound change in the development of the island of São Miguel. It resulted in the economic, social and political migration of settlers from the municipality of Vila Franca and the growth of the city of Ponta Delgada, then an economic rival in the region.
- Gaspar Frutuoso, Saudades da Terra, (2005)
- Dina Silveira, Caracterização da sismicidade histórica da ilha de S. Miguel com base na reinterpretação de dados de macrossísmica: contribuição para a valiação do risco sísmico. Tese de Mestrado em Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, 149 p., 2002.
- Rui Marques, Movimentos de Vertente do Sismo de 1522?, Centro de Vulcanologia e Avaliação de Riscos Geológicos (CVARG), Universidade dos Açores, Ponta Delgada, 2006.
- Silva Ribeiro, Luís da (1951), "O romance de algumas mágoas do terramoto de Vila-Franca em 1522", Boletim do Instituto Histórico da Ilha Terceira (in Portuguese), 9, Angra do Heroísmo (Azores), Portugal, p. 104
- Bento, Carlos Melo (2008), História dos Açores: Da descoberta a 1934 (in Portuguese), Ponta Delgada (Azores), Portugal: Câmara Municipal de Ponta Delgada
- d'Oliveira, Manuel da Sousa (1990), Escavações Arqueológicas em Vila Franca do Campo 1967-1982 (in Portuguese)