The 1867 Virgin Islands earthquake and tsunami occurred on November 18, at 2.45 p.m. in the Anegada Trough about 20 km southwest of Saint Thomas,

Danish West Indies The Danish West Indies ( da, Dansk Vestindien) or Danish Antilles or Danish Virgin Islands were a Danish colonization of the Americas, Danish colony in the Caribbean, consisting of the islands of Saint Thomas, U.S. Virgin Islands, Saint Thomas ...

(now U.S. Virgin Islands). The 7.5 earthquake came just 20 days after the devastating San Narciso Hurricane in the same region. Tsunamis from this earthquake were some of the highest ever recorded in the

Lesser Antilles The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc betwe ...

. Wave heights exceeded in some islands in the

. The earthquake and tsunami resulted in no more than 50 fatalities, although casualties in the hundreds is also claimed.

Tectonic setting

The U.S.Virgin Islands are part of the

Greater Antilles The Greater Antilles ( es, Grandes Antillas or Antillas Mayores; french: Grandes Antilles; ht, Gwo Zantiy; jam, Grieta hAntiliiz) is a grouping of the larger islands in the Caribbean Sea, including Cuba, Hispaniola, Puerto Rico, Jamaica, and ...

that lies parallel to the

Puerto Rico Trench The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench, the deepest in the Atlantic, is associated with a complex transition between the Lesser Antilles subduction zone to the sou ...

; an oblique

subduction zone Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

where the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...

is underthrusted beneath the

Caribbean Plate The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America. Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders ...

along the

Lesser Antilles subduction zone The Lesser Antilles subduction zone is a convergent plate boundary on the seafloor along the eastern margin of the Lesser Antilles Volcanic Arc. In this subduction zone, oceanic crust of the South American Plate is being subducted under the Cari ...

transits to

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

along the

Septentrional-Oriente fault zone The Septentrional-Orient fault zone (SOFZ) is a system of active coaxial left lateral-moving strike slip faults that runs along the northern side of the island of Hispaniola where Haiti and the Dominican Republic are located and continues along ...

. Because of this transition, the overriding Caribbean Plate begins to extend, and normal faults starts to break out as a result. Subduction and shallow crustal faults pose earthquake and tsunami risk to the area, although the Lesser Antilles

megathrust Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqu ...

has not seen any major earthquake along its subduction interface. A possible earthquake along the megathrust may have been the 8.3, 1843 Guadeloupe earthquake.

Earthquake

The earthquake consisted of two shocks, 10 minutes apart, and the two tsunamis came 10 minutes after each shock. Shaking reportedly lasted a minute in

Frederiksted Frederiksted is both the town and one of the two administrative districts of St. Croix, U.S. Virgin Islands. It is a grid-planned city, designed by surveyor Jens Beckfor, originally to 14x14 blocks but built 7x7 to enhance the island commerce in ...

, where the earthquake stirred a dust cloud that blanketed the town. Shaking reached intensity IX on the

Rossi–Forel scale The Rossi–Forel scale was one of the first seismic scales to represent earthquake intensities. Developed by Michele Stefano de Rossi, Michele Stefano Conte de Rossi of Italy and François-Alphonse Forel of Switzerland during the late 19th century ...

in the Danish West Indies. Rossi–Forel IX-level shaking was also felt on the British Virgin Islands, Puerto Rico and U.S. Virgin Islands. Survivor accounts stated that there were two distinct shocks 10–15 minutes apart. On the Modified Mercalli intensity scale, the intensity ranged from VIII (''Severe'') to X (''Extreme''). An

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

with a magnitude of 6.5 occurred on March 17, 1868. There is uncertainty about its timing of occurrence, either 07:15 or 19:15 local time as several reports documented it happening in the morning while one reported it in the "evening". Most likely it occurred in the morning and "evening" was a typographical error. It was felt with a maximum Modified Mercalli intensity of VII (''Very strong'') and a tsunami accompanied the shock.

Tsunami

At Saint Thomas, the first wave was described as a "straight white wall, about 15 to 23 feet (4.6 to 7.0 meters)" which advanced to the harbor, 10 minutes after the earthquake. The wave picked up steamers along the way and broke to just a few feet in front of the town. The run-up height was across the town. A smaller wave came shortly and penetrated further in the island. Thirty people perished when the waves swept them away. Run-ups of were recorded at Charlotte Amalie, where 12 people died. The La Plata, a steamship serving the

Royal Mail Steam Packet Company The Royal Mail Steam Packet Company was a British shipping company founded in London in 1839 by a Scot, James MacQueen. The line's motto was ''Per Mare Ubique'' (everywhere by sea). After a troubled start, it became the largest shipping group ...

was swamped by the tsunami, killing nearly all of its crew onboard. Little Saba saw the highest waves at . A US Navy ship which had arrived the day before, the USS De Soto, was ripped from her moorings and beached. The second wave then brought the ship with her bottom seriously damaged back to sea. At Christiansted,

Saint Croix Saint Croix; nl, Sint-Kruis; french: link=no, Sainte-Croix; Danish and no, Sankt Croix, Taino: ''Ay Ay'' ( ) is an island in the Caribbean Sea, and a county and constituent district of the United States Virgin Islands (USVI), an unincorpo ...

, the 7–9-meter waves drowned five people and inundated the island up to 90 meters inland. The tsunami destroyed 20 houses and stranded numerous boats inland. In some parts of the island, the waves reached a run-up height of 14.6 meters.

on the same island was hit by waves up to 7.6 meters. The surging seawater beached many vessels including a US Navy ship, '' USS Monongahela'' along the beaches of Frederiksted. The tsunami waves were 12 meters on Water Island. Meanwhile, at

Road Town Road Town, located on Tortola, is the capital of the British Virgin Islands. It is situated on the horseshoe-shaped Road Harbour in the centre of the island's south coast. The population was about 15,000 in 2018. The name is derived from the na ...

British Virgin Islands ) , anthem = "God Save the King" , song_type = Territorial song , song = "Oh, Beautiful Virgin Islands" , image_map = File:British Virgin Islands on the globe (Americas centered).svg , map_caption = , mapsize = 290px , image_map2 = Brit ...

, the waves were between and meters which swept away much of the low-lying towns. In

Antigua Antigua ( ), also known as Waladli or Wadadli by the native population, is an island in the Lesser Antilles. It is one of the Leeward Islands in the Caribbean region and the main island of the country of Antigua and Barbuda. Antigua and Bar ...

, the sea level rose at Saint John harbor. Eyewitnesses in

Basse-Terre Basse-Terre (, ; ; gcf, label=Guadeloupean Creole, Bastè, ) is a commune in the French overseas department of Guadeloupe, in the Lesser Antilles. It is also the ''prefecture'' (capital city) of Guadeloupe. The city of Basse-Terre is located ...

Guadeloupe Guadeloupe (; ; gcf, label=Antillean Creole, Gwadloup, ) is an archipelago and overseas department and region of France in the Caribbean. It consists of six inhabited islands—Basse-Terre, Grande-Terre, Marie-Galante, La Désirade, and the ...

saw the sea receding and returning, flooding the place up to . Deshayes was hit with very high waves, an estimated in height and a length of 5 km. The tsunami swept away many personal belongings and items. In Saint-Rose however, the waves were determined to be no more than when a church said to house fleeing survivors located 10 meters above sea-level remained undamaged. In Puerto Rico, wave heights of meters swept through the island's coast. A parish church in Bayamón barrio-pueblo was damaged as a result of the earthquake.

Scientific analysis

Little research has been made to study the earthquake and tsunami in detail. Tsunami deposits on Saint Thomas left in salt ponds and lagoons have not been extensively studied. This despite the fact that the Caribbean has over 124 reported tsunamis or tsunami-like events since 1498, 27 of them have resulted in fatalities. A study by Zahibo and others published a

surface-wave magnitude The surface wave magnitude (M_s) scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This ma ...

of 7.5 () at a

hypocenter In seismology, a hypocenter or hypocentre () is the point of origin of an earthquake or a subsurface nuclear explosion. A synonym is the focus of an earthquake. Earthquakes An earthquake's hypocenter is the position where the strain energy s ...

depth of less than . The source of the earthquake is located in the

Anegada Passage The Anegada Passage is a strait in the Caribbean that separates the British Virgin Islands and the British ruled Sombrero, Anguilla, Sombrero Island of Anguilla, and connects the Caribbean and the Atlantic Ocean. It is 2300 m deep. Because the ...

. The Reid Fault located south of Saint Thomas on the northern scarp of the Anegada Trough runs for seven tens of kilometers may have ruptured and produced slip no greater than ten meter. The rupture may have initiated at a depth of 3 km along this

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

. An

underwater landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting s ...

triggered by movement on the seafloor would likely be the primary source of the tsunami as the run-up heights of the tsunami were unusually high, and these waves arrived almost immediately after the quake. Computer-run simulations of the tsunami suggest the earthquake ruptured a steeply-dipping (70°), by fault with a focus depth of . The simulation indicated a maximum slip of . Another simulation of the earthquake and tsunami suggest the rupture was only 50 km in length, corresponding to a 7.2 earthquake.

References

{{Earthquakes in the Caribbean 1867 earthquakes Tsunamis in the United States Earthquakes in the Caribbean Earthquakes in Denmark Earthquakes in Puerto Rico 1867 disasters in the United States 1867 floods 1867 in the British Empire 1867 in Puerto Rico 1867 in the British Virgin Islands 1867 in the Caribbean Natural disasters in the British Virgin Islands Natural disasters in British Overseas Territories 1867 natural disasters in the United States Maritime incidents in November 1867 1867 disasters in North America

Tectonic setting

Earthquake

Tsunami

Scientific analysis

See also

References