1799 Vendée Earthquake
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The 1799 Vendée earthquake (french: Séisme de 1799 dans le Marais breton-vendéen) or Bouin earthquake was a
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
6.4
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
that struck the
Vendée Vendée (; br, Vande) is a department in the Pays de la Loire region in Western France, on the Atlantic coast. In 2019, it had a population of 685,442.
area of western France on 25 January 1799 (6
Pluviôse Pluviôse (; also ''Pluviose'') was the fifth month in the French Republican Calendar. The month was named after the Latin word ''pluviosus'', which means ''rainy''. Pluviôse was the second month of the winter quarter (''mois d'hiver''), star ...
of year VII in the French Republican calendar) with aftershocks on the following days. Its
epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...
was located at a depth of 24 km in the
Bay of Bourgneuf The Bay of Bourgneuf (french: Baie de Bourgneuf, ) is a bay situated on the French Atlantic coast, at the border of the Loire-Atlantique and Vendée departments. In the Middle Ages the bay was known as the ''baie de Bretagne'' or ''baye de Bretagn ...
at the level of the island of Bouin. Shocks of intensity VII–VIII were felt throughout the west of France.


Location

The
passage du Gois The () or is a causeway between Beauvoir-sur-Mer and the island of Noirmoutier, in Vendée on the Atlantic coast of France. The causeway is long and is flooded twice a day by the high tide. A road runs along the causeway. Every year, a foot ...
, in the
Bay of Bourgneuf The Bay of Bourgneuf (french: Baie de Bourgneuf, ) is a bay situated on the French Atlantic coast, at the border of the Loire-Atlantique and Vendée departments. In the Middle Ages the bay was known as the ''baie de Bretagne'' or ''baye de Bretagn ...
, links
Beauvoir-sur-Mer Beauvoir-sur-Mer (, literally ''Beauvoir on Sea'') is a commune in the Vendée department in the administrative region of the Pays de la Loire, France. See also *Communes of the Vendée department The following is a list of the 257 communes ...
on the mainland to
Barbâtre Barbâtre () is a commune in the Vendée department in the Pays de la Loire region in western France. Geography The altitude of the commune of Barbâtre lies between 0 and 19 meters. The area of the commune is 12.47 km2. Arms The arms ...
on the île de Noirmoutier. Another reference in terms of regional seismicity is the 1972 earthquake on the island of
Oléron The Isle of Oléron or Oléron Island (french: île d'Oléron, ; Saintongese: ''ilâte d'Olerun''; oc, illa d'Olairon or ; la, Uliarus insula, ) is an island off the Atlantic coast of France (due west of Rochefort), on the southern side of the ...
in
and in . The earthquake of 25 January 1799 was located in the Marais Breton marshland, a wetland located on the coast of the Atlantic Ocean which marks the limit between the two former
French provinces The Kingdom of France was organised into provinces until the National Constituent Assembly adopted a more uniform division into departments (''départements'') and districts in late 1789. The provinces continued to exist administratively until 2 ...
of
Brittany Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo language, Gallo: ''Bertaèyn'' ) is a peninsula, Historical region, historical country and cultural area in the west of modern France, covering the western part of what was known ...
and
Poitou Poitou (, , ; ; Poitevin: ''Poetou'') was a province of west-central France whose capital city was Poitiers. Both Poitou and Poitiers are named after the Pictones Gallic tribe. Geography The main historical cities are Poitiers (historical c ...
and extends over the two departments of
Loire-Atlantique Loire-Atlantique (; br, Liger-Atlantel; before 1957: ''Loire-Inférieure'', br, Liger-Izelañ, link=no) is a department in Pays de la Loire on the west coast of France, named after the river Loire and the Atlantic Ocean. It had a population o ...
and
Vendée Vendée (; br, Vande) is a department in the Pays de la Loire region in Western France, on the Atlantic coast. In 2019, it had a population of 685,442.
in the
French region France is divided into eighteen administrative regions (french: régions, singular ), of which thirteen are located in metropolitan France (in Europe), while the other five are overseas regions (not to be confused with the overseas collecti ...
of
Pays de la Loire Pays de la Loire (; ; br, Broioù al Liger) is one of the 18 regions of France, in the west of the mainland. It was created in the 1950s to serve as a zone of influence for its capital, Nantes, one of a handful of "balancing metropolises" (). ...
. The epicenter was located at sea, in the
bay of Bourgneuf The Bay of Bourgneuf (french: Baie de Bourgneuf, ) is a bay situated on the French Atlantic coast, at the border of the Loire-Atlantique and Vendée departments. In the Middle Ages the bay was known as the ''baie de Bretagne'' or ''baye de Bretagn ...
, between
Barbâtre Barbâtre () is a commune in the Vendée department in the Pays de la Loire region in western France. Geography The altitude of the commune of Barbâtre lies between 0 and 19 meters. The area of the commune is 12.47 km2. Arms The arms ...
at the entrance to the island of
Noirmoutier Noirmoutier (also French language, French: Île de Noirmoutier, ; br, Nervouster, ) is a tidal island off the Atlantic Ocean, Atlantic coast of France in the Vendée Departments of France, department (85). History Noirmoutier was the locatio ...
and Bouin on the mainland. The most significant damage occurred in Bouin,
Machecoul Machecoul ( br, Machikoul) is a former commune in the Loire-Atlantique department in western France. On 1 January 2016, it was merged into the new commune of Machecoul-Saint-Même.Bois-de-Céné,
La Garnache La Garnache () is a commune in the Vendée department in the Pays de la Loire region in western France. Population See also *Communes of the Vendée department *François de Charette François Athanase de Charette de la Contrie (2 May 17 ...
,
Beauvoir-sur-Mer Beauvoir-sur-Mer (, literally ''Beauvoir on Sea'') is a commune in the Vendée department in the administrative region of the Pays de la Loire, France. See also *Communes of the Vendée department The following is a list of the 257 communes ...
and Barbâtre areas. The earthquake was felt all along the coast, as far as
Vannes Vannes (; br, Gwened) is a commune in the Morbihan department in Brittany in north-western France. It was founded over 2,000 years ago. History Celtic Era The name ''Vannes'' comes from the Veneti, a seafaring Celtic people who lived ...
in the north and
La Rochelle La Rochelle (, , ; Poitevin-Saintongeais: ''La Rochéle''; oc, La Rochèla ) is a city on the west coast of France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime department. With ...
in the south, and up to a distance of one hundred and fifty to two hundred kilometres inland. The
Grand-Ouest The Grand-Ouest is a geographical area of France that encompasses Brittany and Pays de la Loire. Traditionally, this area has a very agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was ...
of France was shaken from Brittany to Normandy, from
Berry A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples are strawberries, raspb ...
to
Anjou Anjou may refer to: Geography and titles France *County of Anjou, a historical county in France and predecessor of the Duchy of Anjou **Count of Anjou, title of nobility *Duchy of Anjou, a historical duchy and later a province of France **Duke ...
and
Touraine Touraine (; ) is one of the traditional provinces of France. Its capital was Tours. During the political reorganization of French territory in 1790, Touraine was divided between the departments of Indre-et-Loire, :Loir-et-Cher, Indre and Vie ...
, from
Limousin Limousin (; oc, Lemosin ) is a former administrative region of southwest-central France. On 1 January 2016, it became part of the new administrative region of Nouvelle-Aquitaine. It comprised three departments: Corrèze, Creuse, and Haute-Vienn ...
to
Poitou Poitou (, , ; ; Poitevin: ''Poetou'') was a province of west-central France whose capital city was Poitiers. Both Poitou and Poitiers are named after the Pictones Gallic tribe. Geography The main historical cities are Poitiers (historical c ...
, from
Saintonge Saintonge may refer to: *County of Saintonge, a historical province of France on the Atlantic coast *Saintonge (region), a region of France corresponding to the historical province Places *Saint-Genis-de-Saintonge, a commune in the Charente-Mari ...
to
Aunis Aunis () is a historical province of France, situated in the north-west of the department of Charente-Maritime. Its historic capital is La Rochelle, which took over from Castrum Allionis (Châtelaillon) the historic capital which gives its name ...
and , in
Auvergne Auvergne (; ; oc, label=Occitan, Auvèrnhe or ) is a former administrative region in central France, comprising the four departments of Allier, Puy-de-Dôme, Cantal and Haute-Loire. Since 1 January 2016, it has been part of the new region Auverg ...
, in the
Morvan The Morvan (historically Morvand from the Latin ''Murvinnum'' 590)Pierre-Henri Billy, ''Dictionnaire des noms de lieux de la France'', éditions Errance, 640 pages, 2011 , is a mountainous massif lying just to the west of the Côte d'Or escarp ...
and as far as
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.


Characteristics

The earthquake of 25 January 1799 is one of the major events of the of France. By its magnitude and intensity of VIII, maximum for the
Armorican Massif The Armorican Massif (french: Massif armoricain, ) is a geologic massif that covers a large area in the northwest of France, including Brittany, the western part of Normandy and the Pays de la Loire. It is important because it is connected to Do ...
, it constitutes the most important earthquake recorded to date in this region and it is one of the six historic earthquakes to have had destructive effects in metropolitan France along with those from Basel near the French border (intensity IX–X) in 1356, , Remiremont (intensity VIII) in 1682, from the Ligurian sea off the Côte d'Azur (intensity X) in 1887 and Lambesc (intensity IX) in 1909 that of being the first earthquake with destructive effect in mainland France to be documented by instrumental seismicity. The 6 Pluviose of the Year VII of the
Republic A republic () is a "state in which power rests with the people or their representatives; specifically a state without a monarchy" and also a "government, or system of government, of such a state." Previously, especially in the 17th and 18th c ...
, around 4 am, the population of the Vendée was suddenly awakened by the earthquake that would add its ruins to those of a region already hit by the
War in the Vendée The war in the Vendée (french: link=no, Guerre de Vendée) was a counter-revolution from 1793 to 1796 in the Vendée region of France during the French Revolution. The Vendée is a coastal region, located immediately south of the river Loir ...
still nearby and by the harsh climatic conditions of the winter of 1799. In Bouin the duration of the tremor was a "half-minute" and its direction from south to north. Several recent studies have made it possible to estimate the magnitude at 6.4 and the depth at 24 km, estimates adopted by the Bureau of Geological and Mining Research. The intensity was of the order of VII–VIII at the epicenter, the centre of the tremor not being located in the heart of the marshland as initially advanced but more to the west, at sea, in the
bay of Bourgneuf The Bay of Bourgneuf (french: Baie de Bourgneuf, ) is a bay situated on the French Atlantic coast, at the border of the Loire-Atlantique and Vendée departments. In the Middle Ages the bay was known as the ''baie de Bretagne'' or ''baye de Bretagn ...
. In the hardest hit area, the earthquake is estimated to have reached intensity VIII due to the lower resistance of the sediments making up the marsh, which locally amplified the seismic movement. Intensity decreases with increasing distance but remained significant in
Nantes Nantes (, , ; Gallo: or ; ) is a city in Loire-Atlantique on the Loire, from the Atlantic coast. The city is the sixth largest in France, with a population of 314,138 in Nantes proper and a metropolitan area of nearly 1 million inhabita ...
and
Les Sables-d'Olonne Les Sables-d'Olonne (; French meaning: "The Sands of Olonne"; Poitevin: ''Lés Sablles d'Oloune'') is a seaside town in Western France, on the Atlantic Ocean. A subprefecture of the department of Vendée, Pays de la Loire, it has the administ ...
(VI–VII),
La Rochelle La Rochelle (, , ; Poitevin-Saintongeais: ''La Rochéle''; oc, La Rochèla ) is a city on the west coast of France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime department. With ...
,
Ile d'Oléron Ile may refer to: * iLe, a Puerto Rican singer * Ile District (disambiguation), multiple places * Ilé-Ifẹ̀, an ancient Yoruba city in south-western Nigeria * Interlingue (ISO 639:ile), a planned language * Isoleucine, an amino acid * Another n ...
and Belle-Île-en-Mer (VI). It was still V–IV in
Tours Tours ( , ) is one of the largest cities in the region of Centre-Val de Loire, France. It is the Prefectures in France, prefecture of the Departments of France, department of Indre-et-Loire. The Communes of France, commune of Tours had 136,463 ...
,
Guernsey Guernsey (; Guernésiais: ''Guernési''; french: Guernesey) is an island in the English Channel off the coast of Normandy that is part of the Bailiwick of Guernsey, a British Crown Dependency. It is the second largest of the Channel Islands ...
,
Vannes Vannes (; br, Gwened) is a commune in the Morbihan department in Brittany in north-western France. It was founded over 2,000 years ago. History Celtic Era The name ''Vannes'' comes from the Veneti, a seafaring Celtic people who lived ...
,
Châteauroux Châteauroux (; ; oc, Chasteurós) is the capital city of the French department of Indre, central France and the second-largest town in the province of Berry, after Bourges. Its residents are called ''Castelroussins'' () in French. Climate Ch ...
,
Rennes Rennes (; br, Roazhon ; Gallo: ''Resnn''; ) is a city in the east of Brittany in northwestern France at the confluence of the Ille and the Vilaine. Rennes is the prefecture of the region of Brittany, as well as the Ille-et-Vilaine department ...
and
Limoges Limoges (, , ; oc, Lemòtges, locally ) is a city and Communes of France, commune, and the prefecture of the Haute-Vienne Departments of France, department in west-central France. It was the administrative capital of the former Limousin region ...
and weaker (III) but still felt in
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...
,
Bordeaux Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefectur ...
or
Caen Caen (, ; nrf, Kaem) is a commune in northwestern France. It is the prefecture of the department of Calvados. The city proper has 105,512 inhabitants (), while its functional urban area has 470,000, Several aftershocks occurred in the sector of Bouin and Machecoul, on 27 and 28 January, then on 5 and 6 February. The variations in the movement of the waters of the region demonstrate that the earthquake was indeed underwater and that it may have given rise to a tsunami.


Probable cause

The collision between the
Aquitaine Aquitaine ( , , ; oc, Aquitània ; eu, Akitania; Poitevin-Saintongeais: ''Aguiéne''), archaic Guyenne or Guienne ( oc, Guiana), is a historical region of southwestern France and a former administrative region of the country. Since 1 January ...
and Armorican
tectonic plates Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
gave birth in the
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
period to the
Hercynian The Variscan or Hercynian orogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea. Nomenclature The name ''Variscan'', come ...
basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...
of the Armorican massif creating faults oriented north-west, south-east, which go from the
Pointe du Raz The Pointe du Raz is a promontory that extends into the Atlantic from western Brittany, in France. The local Breton name is ''Beg ar Raz''. It is the western point of the ''commune'' of Plogoff, Finistère. It is named after the ''Raz de Sein'', ...
to Nantes and the to
Angers Angers (, , ) is a city in western France, about southwest of Paris. It is the prefecture of the Maine-et-Loire department and was the capital of the province of Anjou until the French Revolution. The inhabitants of both the city and the prov ...
and extend south of the Loire estuary. These shear fractures are at the origin of
grabens In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...
which are accentuated during the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
and the
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
, and fill up with
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
s that may be more than 100 m thick in the deepest ditches. They are still active in the
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
and their replay explains the earthquakes of the south of the Loire and more particularly those of the Vendée. The municipalities where the greatest damage was reported (Bouin, Machecoul) are close to these fractures, as are the localities where the earthquake was felt with force even if the damage was less (
Champtoceaux Champtoceaux () is a former commune in the Maine-et-Loire department of western France. On 15 December 2015, it was merged into the new commune Orée-d'Anjou.Beauvoir-sur-Mer Beauvoir-sur-Mer (, literally ''Beauvoir on Sea'') is a commune in the Vendée department in the administrative region of the Pays de la Loire, France. See also *Communes of the Vendée department The following is a list of the 257 communes ...
,
Saint-Gilles-Croix-de-Vie Saint-Gilles-Croix-de-Vie () is a commune in the Vendée department, region of Pays de la Loire, western France. It is situated on the Côte de Lumière. The community originated in 1967 from the unification of two communities on either side o ...
,
Nantes Nantes (, , ; Gallo: or ; ) is a city in Loire-Atlantique on the Loire, from the Atlantic coast. The city is the sixth largest in France, with a population of 314,138 in Nantes proper and a metropolitan area of nearly 1 million inhabita ...
,
La Brière ''La Brière'' (translated as ''Passion and Peat'') is a 1923 novel by Alphonse de Chateaubriant that won the Grand prix du roman de l'Académie française for that year. The novel is set in the rustic fenland landscape west of Nantes, known as ...
,
Tiffauges Tiffauges () is a commune in the Vendée department in the Pays de la Loire region in western France. History Gilles de Rais owned the local fortress. It is the location of a battle between the French Republican troops and the royalists du ...
, and, further on,
La Flèche La Flèche () is a town and commune in the French department of Sarthe, in the Pays de la Loire region in the Loire Valley. It is the sub-prefecture of the South-Sarthe, the chief district and the chief city of a canton, and the second most po ...
). The epicenter was located on the continental shelf off the island of Noirmoutier, in Bourgneuf bay. The earthquake caused a large wave felt in Belle-ÃŽle-en-Mer, La Rochelle and in the Loire Valley.


Damage

In some villages, Bouin and Machecoul in particular, the shock was so violent that many houses cracked or collapsed. In Bouin there were two types of constructions, those of the town, built on a hard limestone hillock in the middle of the marshes and constructed from stones extracted from the hill itself and those of the marsh, built on mudflats - far more fragile buildings which could not be repaired after the shocks. About 6-8% of the total number of houses were close to ruin (14 collapsed and 150 damaged). These were probably the most fragile. Lightweight constructions were not, however, the only buildings affected by the earthquake, as one testimony reports: "the spire of the steeple, all in dressed stone, built with cement, is on the verge of falling". (NB: The author sometimes erroneously refers to the
Marais Poitevin The Marais Poitevin () or Poitevin Marsh is a large area of marshland in western France. The name means "Poitou's Marsh" or the "Marsh of the Poitou region". It is a remnant of what was the former . The western zone near the sea (about two-thi ...
instead of the Marais Breton) The observations made at Machecoul are quite comparable. Here too, it was especially the fragile buildings of the marshes that seem to be the most affected. Most of the houses damaged during the civil war had only been repaired temporarily and were all the more weakened. Damage was also noted in La Garnache, 6 km northeast of
Challans Challans () is a commune in the Vendée department in the Pays de la Loire region in western France. Challans station has rail connections to Saint-Gilles-Croix-de-Vie and Nantes. Population Notable people * Pauline de Lézardière, born ...
, in the Bois-de-Céné marsh area, in Barbâtre, a town which, partly destroyed by the earthquake, lost its title of municipality and was united in Noirmoutier, and
Bourgneuf-en-Retz Bourgneuf-en-Retz (; br, Bourc'hnevez-Raez) is a former commune in the Loire-Atlantique department in western France. On 1 January 2016, it was merged into the new commune of Villeneuve-en-Retz. In the Marais, the towns of Noirmoutier, Beauvoir-sur-Mer and Saint-Gilles-Croix-de-Vie strongly felt the tremors without any damage being reported however. In the neighbouring areas of the Marais, fairly detailed information on the effects of the earthquake was reported for Nantes, Saint-Lyphard en Brière, Tiffauges, around the
Lac de Grand-Lieu Lac de Grand-Lieu () is a lake located to the southwest of Nantes, in the Loire-Atlantique, France, and almost entirely in Saint-Philbert-de-Grand-Lieu. At an elevation of , its surface area is , making it the largest lake in France in winter, bu ...
, near the Temple but also for the municipalities of the neighbouring departments like
Vannes Vannes (; br, Gwened) is a commune in the Morbihan department in Brittany in north-western France. It was founded over 2,000 years ago. History Celtic Era The name ''Vannes'' comes from the Veneti, a seafaring Celtic people who lived ...
and
Josselin Josselin (; ) is a commune in the Morbihan department in Brittany in north-western France. History St Meriadek is said to have founded a chapel there during the 4th century. Much later Josselin became a stronghold of the House of Rohan. An ...
in
Morbihan Morbihan ( , ; br, Mor-Bihan ) is a department in the administrative region of Brittany, situated in the northwest of France. It is named after the Morbihan (''small sea'' in Breton), the enclosed sea that is the principal feature of the coastli ...
,
Le Mans Le Mans (, ) is a city in northwestern France on the Sarthe River where it meets the Huisne. Traditionally the capital of the province of Maine, it is now the capital of the Sarthe department and the seat of the Roman Catholic diocese of Le Man ...
,
La Flèche La Flèche () is a town and commune in the French department of Sarthe, in the Pays de la Loire region in the Loire Valley. It is the sub-prefecture of the South-Sarthe, the chief district and the chief city of a canton, and the second most po ...
,
La Ferté-Bernard La Ferté-Bernard () is a commune in the Sarthe department in the Pays de la Loire region in north-western France. History La Ferté-Bernard owes its origin and name to a stronghold (''fermeté'') built about the 11th century and afterwards held ...
in
Sarthe Sarthe () is a department of the French region of Pays de la Loire, and the province of Maine, situated in the ''Grand-Ouest'' of the country. It is named after the river Sarthe, which flows from east of Le Mans to just north of Angers. It had ...
,
Angers Angers (, , ) is a city in western France, about southwest of Paris. It is the prefecture of the Maine-et-Loire department and was the capital of the province of Anjou until the French Revolution. The inhabitants of both the city and the prov ...
,
Beaufort-en-Vallée Beaufort-en-Vallée () is a former commune in the Maine-et-Loire department in western France. On 1 January 2016, it was merged into the new commune of Beaufort-en-Anjou.Maine-et-Loire Maine-et-Loire () is a department in the Loire Valley in the Pays de la Loire region in Western France. It is named after the two rivers, Maine and the Loire. It borders Mayenne and Sarthe to the north, Loire-Atlantique to the west, Indre-e ...
,
Rennes Rennes (; br, Roazhon ; Gallo: ''Resnn''; ) is a city in the east of Brittany in northwestern France at the confluence of the Ille and the Vilaine. Rennes is the prefecture of the region of Brittany, as well as the Ille-et-Vilaine department ...
,
La Guerche La Guerche () is a commune in the Indre-et-Loire department in central France. Population People from La Guerche are called ''Guerchois''. Popular culture Louis Amédée Achard, an author created a character called Monsieur of La Guerche, who ...
in
Ille-et-Vilaine Ille-et-Vilaine (; br, Il-ha-Gwilen) is a department of France, located in the region of Brittany in the northwest of the country. It is named after the two rivers of the Ille and the Vilaine. It had a population of 1,079,498 in 2019.
,
La Rochelle La Rochelle (, , ; Poitevin-Saintongeais: ''La Rochéle''; oc, La Rochèla ) is a city on the west coast of France and a seaport on the Bay of Biscay, a part of the Atlantic Ocean. It is the capital of the Charente-Maritime department. With ...
in
Charente-Maritime Charente-Maritime () is a department in the Nouvelle-Aquitaine region on the southwestern coast of France. Named after the river Charente, its prefecture is La Rochelle. As of 2019, it had a population of 651,358 with an area of 6,864 square kil ...
. Significant water movements are indicated by letters and newspaper articles: flooding, submersion of dykes, strong wave shaking boats, abnormal rises of rivers, etc., south of the Loire as near Bouin (submersion of dykes and wave), in Bourgneuf (waves and land transport), in La Rochelle (wave) as well as in the north of the Loire as in Nantes (waves), in Brière near Saint-Nazaire (water movements) or again at Belle-Île-en-Mer (dyke submersion). Some of the water movements, in particular floods and abnormal rises in rivers, are of dubious cause. They could equally be explained by a sudden thaw removing the ice dams in the rivers reported a few weeks earlier as by a tidal wave. Other observations, made just after the earthquake (strong wave shaking the boats, submersion of the dikes), are more convincing. They seem to show that the epicenter of the earthquake was at sea and not around Bouin as first thought. This wave and these submersions could be due to a tsunami.


Consequences on the local economy

Beyond the destruction of buildings and superstructures, the more or less long-term consequences of the earthquake on the local economy were reported in particular to the central administration of
Loire-Inférieure Loire-Atlantique (; br, Liger-Atlantel; before 1957: ''Loire-Inférieure'', br, Liger-Izelañ, link=no) is a department in Pays de la Loire on the west coast of France, named after the river Loire and the Atlantic Ocean. It had a population of ...
by the municipal administration of
Herbignac Herbignac (; Gallo: ''Èrbinyac'', br, Erbigneg) is a commune in the Loire-Atlantique department in western France. Population See also *Château de Ranrouët *La Baule - Guérande Peninsula *Communes of the Loire-Atlantique department The ...
which indicates the 1st March 1799 (11 Ventose year VII) that the population of the municipalities of La Briere in St-Hyphard and Herbignac that "... usually draw clods which are used for heating the township and still supply all the surrounding townships and allow them to live for two thirds of the year" showed losses caused by the earthquake. Likewise, the municipal administration of Machecoul pointed out that if the owners succeeded in partially re-establishing the crops destroyed by the civil war, they had not yet derived any benefit from it at the date of the earthquake and that "the lowlands both in the upper and lower marshes of the municipality de Machecoul will not yet produce anything this year, these lands have been under water for more than two months, the wheat will be rotten like last year".


Informing the authorities

The Commissioners of the Directory such as Sieur Mignon, Commissioner of the executive board for the canton of Bouin, informed the "Citizen Minister" of the event. The central administration of Loire-Inférieure was quickly warned of the significant damage suffered in the town of Machecoul. From the coast and up to a distance of one hundred and fifty to two hundred kilometers inland, the earthquake created such a commotion that the central administration near all the departments close to the earthquake did not fail to inform the Minister of the Interior, from Nantes, Laval, Le Mans, Tours, Poitiers, Châteauroux, Fontenay-le-Comte, Châteaubriant, etc.


Press coverage

The local press, ''Le Publicateur de Nantes'', ''La Feuille Nantes'', ''Les Étrennes de Nantes'', ''L'Ami de la liberté'', ''La Feuille du jour'', etc. recount the event over several days, relayed by the national press, ''Le Bien Informé'', ''La Gazette nationale'', ''Les Annales de la République''. In this period of development of the written press, these pages are important sources of information for future seismology when the original records are lost: they indeed publish the testimonies and the communiques of the authorities, directly or with the hindsight and analysis of their own.


Testimonials

The writings which relate the effects of the earthquake are marked by the proximity of the Vendée War which ravaged the region, and must be considered in this historical framework. The letters from the local administrators describe the damage most accurately and precisely. Newspapers can provide additional insight, but their information should be examined with caution.


Other earthquakes in the region

No other example of an earthquake of such magnitude has been identified in the area The only tremors recorded are minor and were noted on the island of Noirmoutier (23 August 1747, 5 February 1833, 15 October 1945 and 22 June 2005) and Bourgneuf-en-Retz (7 April 1767). On the Atlantic coast near the marsh, however, approaching tremors were noted at Vannes (intensity VII) on 9 January 1930, in Quimper (intensity VII) on 2 January 1959 and on the island of
Oléron The Isle of Oléron or Oléron Island (french: île d'Oléron, ; Saintongese: ''ilâte d'Olerun''; oc, illa d'Olairon or ; la, Uliarus insula, ) is an island off the Atlantic coast of France (due west of Rochefort), on the southern side of the ...
(intensity VII), 7 September 1972.


Contemporary projections

Bouin, like all the communes of the Vendée and the 146 communes of the south of Loire-Atlantique, is classified in seismicity zone 3 (moderate risk). The authors of the 2016 Geological and Mining Research Bureau study report "Impact of the 1799 earthquake on current buildings in the departments of Loire-Atlantique (44) and Vendée (85)", modelled the 1799 earthquake in the contemporary setting of the two departments. They estimated damage of the order of 10,000 to 12,000 uninhabitable buildings would occur, i.e. a much larger consequence than at the time due to the urbanisation that has since taken place and in particular on poor quality land on which would reproduce, on buildings constructed before the implementation of the 2011 building regulations, the known effects on the mudflats of the Marais Breton in 1799. In 2019, Caroline Kaub proposed in her thesis to "characterise the geometry of possible plio-Quaternary and potentially active faults in this region, with a particular interest in the Machecoul fault, bordering the sedimentary basins of the Breton Marsh and the Bay of Bourgneuf and potential candidate for the Vendéen earthquake of 1799 uggestingthat the plio-Quaternary sedimentation of the sea and land basins south of the Machecoul fault could be controlled by this fault probably inherited from the Eocene nd in providinga bundle of clues making it possible to link the Machecoul fault to the rupture of the Vendéen earthquake of 1799".. The Bouin earthquake is the for the
Blayais Nuclear Power Plant The Blayais Nuclear Power Plant is a nuclear plant on the banks of the Gironde estuary near Blaye, France operated by Électricité de France. Description The power plant has 4 pressurized water reactors – producing 951 MW gross and 910 ...
.


Notes and references

{{DEFAULTSORT:1799 Vendee earthquake Earthquakes in France History of the Atlantic Ocean 1790s earthquakes 1799 natural disasters History of Vendée History of Loire-Atlantique 1799 in France