The southern part of

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

was struck by a major earthquake on 12 June 1766 at midnight local time. It had an estimated magnitude of 6.8 and a maximum felt intensity of IX (''destructive'') on the

MSK scale MSK may refer to the following: * Common abbreviation for Human musculoskeletal system * ''Marinestosstruppkompanie'', German naval assault troops * Postal code for Marsaskala, Malta * Station code for Marske railway station, England * Medullary spo ...

. 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. Determination The primary purpose of a ...

was offshore, near

Santiago de Cuba Santiago de Cuba is the second-largest city in Cuba and the capital city of Santiago de Cuba Province. It lies in the southeastern area of the island, some southeast of the Cuban capital of Havana. The municipality extends over , and contains t ...

, with a

focal Focal or FOCAL may refer to: *Focal (lexicographical website), an Irish lexicographical website *FOCAL (programming language), a programming language for the PDP-8 and similar machines * Focal (HP-41), for programming HP calculators * FOCAL (space ...

depth of 25 km. Santiago de Cuba suffered the worst damage, although large areas of Cuba were affected. It was felt in both

Havana Havana (; ) is the capital and largest city of Cuba. The heart of La Habana Province, Havana is the country's main port and commercial center.Jamaica Jamaica is an island country in the Caribbean Sea and the West Indies. At , it is the third-largest island—after Cuba and Hispaniola—of the Greater Antilles and the Caribbean. Jamaica lies about south of Cuba, west of Hispaniola (the is ...

(140 km). Between 34 and 40 people died and a further 700 were injured.

Tectonic setting

The southernmost coast of Cuba lies adjacent to the southern margin of the North American plate. This boundary is a major left lateral (sinistral)

transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...

, the Septentrional-Oriente fault zone, where the North American plate is moving westwards relative to the

Gonâve microplate Gonave may refer to: *Gulf of Gonâve *Gonâve Island * Gonâve Microplate See also *Gonaïves Gonaïves (; also Les Gonaïves; , ) is a commune in northern Haiti, and the capital of the Artibonite department of Haiti. The population was 356,3 ...

at a rate of between 6 and 11 mm per year. This fault zone forms the most seismically active part of Cuba.

Earthquake

The earthquake struck at midnight and lasted for between one and a half and seven minutes. From the observed seismic intensities, the epicenter is likely to have been offshore, although its precise location is unknown. The mainshock was followed by a series of

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...

s, that continued for a further 66 days. From its estimated location, it is interpreted to have been caused by rupture of the Septentrional-Oriente fault zone.

Damage

The intensity of shaking was at a maximum at

Morro Castle Morro Castle may refer to: Fortress * Morro Castle (Havana), a fortress guarding Havana Bay, Cuba * Castillo San Felipe del Morro Castillo San Felipe del Morro (English language , English: Promontory Castle of Saint Philip), most commonly known ...

and La Socapa Fort, with an estimated value of IX (''Destructive''), due to their proximity to the epicentre and the presence of thick

alluvial deposits Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

. Levels of VIII (''Damaging'') were reached in the cities of Santiago de Cuba and

Bayamo Bayamo is the capital city of the Granma Province of Cuba and one of the largest cities in the Oriente region. Overview The community of Bayamo lies on a plain by the Bayamo River. It is affected by the violent Bayamo wind. One of the mos ...

. Morro Castle and La Socapa Fort were destroyed as were the hospital and the governor's house. Santiago de Cuba's cathedral was damaged. The earthquake is recorded to have caused the deaths of between 34 and 40 inhabitants, all of them in Santiago de Cuba. A further 700 people were injured.

References

{{Reflist 1760s earthquakes 1766 disasters Earthquakes in Cuba 1760s in Cuba History of Santiago de Cuba Santiago de Cuba Province