The 1868 Arica earthquake was an earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

 that occurred on August 13, 1868, near Arica

Arica

Arica is a city in northern Chile. "Arica" may also refer to:Places* Arica and Parinacota Region, Chile* Arica Airport , Chile* Arica, Amazonas, town in Colombia* Rio Aricá-açu, tributary of the Cuiabá River south of Cuiabá, BrazilOther...

, then part of Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, now part of Chile

Chile

Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

, at 21:30 UTC. It had an estimated magnitude between 8.5 and 9.0. A tsunami

Tsunami

A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 (or multiple tsunamis) in the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 was produced by the earthquake, which was recorded in Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

.

Tectonic setting

The earthquake occurred along the boundary between the Nazca Plate

Nazca Plate

]The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction along the Peru-Chile Trench of the Nazca Plate under the South American Plate is largely responsible for the...

 and the South American Plate

South American Plate

The South American Plate is a continental tectonic plate which includes the continent of South America and also a sizeable region of the Atlantic Ocean seabed extending eastward to the Mid-Atlantic Ridge....

. The earthquake is likely to be a result of thrust-faulting

Thrust fault

A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...

, caused by the subduction

Subduction

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

 of the Nazca plate beneath the South American plate.

The coastal parts of Peru and Chile have a history of great megathrust earthquake

Megathrust earthquake

Megathrust earthquakes occur at subduction zones at destructive plate boundaries , where one tectonic plate is forced under another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, these earthquakes are among the world's largest, with moment magnitudes ...

s originating from this plate boundary, such as the 1960 Valdivia earthquake.

Damage

The earthquake caused the almost complete destruction of Arica, Tacna

Tacna

- Rail :Tacna is served by a cross-border standard gauge railway to Arica, Chile.It is also the location of the National Railway Museum of Peru.-Air:Tacna is served by the Crnl. FAP...

, Moquegua

Moquegua

Moquegua is a city in southern Peru, located in the Moquegua Region, of which it is the regional capital. It is also capital of Mariscal Nieto Province and Moquegua District. It is located 1144 kilometers south from the capital city of Lima.-History:...

, Mollendo

Mollendo

Mollendo is a town bordering the Pacific Ocean in southern Peru. It is located in the Arequipa Region and is the capital of both the Islay Province and the Mollendo District...

, Ilo

Ilo

Ilo is a port city in southern Peru, with some 58,000 inhabitants. It is the largest city in the Moquegua Region and capital of the province of Ilo.-History:...

, Iquique

Iquique

Iquique is a port city and commune in northern Chile, capital of both the Iquique Province and Tarapacá Region. It lies on the Pacific coast, west of the Atacama Desert and the Pampa del Tamarugal. It had a population of 216,419 as of the 2002 census...

, Torata

Torata District

Torata District is one of six districts of the province Mariscal Nieto in Moquegua Region, Peru.- External links :*...

 and Arequipa

Arequipa

Arequipa is the capital city of the Arequipa Region in southern Peru. With a population of 836,859 it is the second most populous city of the country...

, giving rise to an estimated 25,000 casualties.

The tsunami drove three ships that had been anchored in the port nearly 800 m inland: the 1560-ton Peruvian corvette

Corvette

A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft or fast attack craft , although many recent designs resemble frigates in size and role...

 America, the U.S. gunboat Wateree

USS Wateree (1863)

The first USS Wateree was a sidewheel gunboat in the United States Navy during the American Civil War.Wateree was built at Chester, Pennsylvania, by Reaney, Son & Archbold; launched on August 12, 1863; and commissioned at the Philadelphia Navy Yard on January 20, 1864, Comdr. F. E...

 and the U.S. store ship Fredonia, which was completely destroyed in the process. The English brig

Brig

A brig is a sailing vessel with two square-rigged masts. During the Age of Sail, brigs were seen as fast and manoeuvrable and were used as both naval warships and merchant vessels. They were especially popular in the 18th and early 19th centuries...

 Chañarcillo and two Chilean schooner

Schooner

A schooner is a type of sailing vessel characterized by the use of fore-and-aft sails on two or more masts with the forward mast being no taller than the rear masts....

s, Rosa Rivera and Regalon were also lost. The tsunami also caused the near complete destruction of the port city of Pisco

Pisco, Peru

Pisco is a city located in the Ica Region of Peru, the capital of the Pisco Province. The city is around 9 metres above sea level. Originally the villa of Pisco was founded in 1640, close to the indigenous emplacement of the same name...

.

The tsunami caused considerable damage in Hawaii, washing out a bridge along the Waiohi river. In New Zealand, substantial damage occurred on the Chatham Islands

Chatham Islands

The Chatham Islands are an archipelago and New Zealand territory in the Pacific Ocean consisting of about ten islands within a radius, the largest of which are Chatham Island and Pitt Island. Their name in the indigenous language, Moriori, means Misty Sun...

 and the Banks peninsula

Banks Peninsula

Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately and encompasses two large harbours and many smaller bays and coves...

 with many houses washed away and boats damaged, but only one death was recorded.

Earthquake

Two separate earthquakes have been described, but they may both be referring to the same event.

The earthquake was felt over a very wide area, up to 1400 km to the northwest in Samanco

Samanco District

Samanco District is one of nine districts of the province Santa in Peru.-References:...

, Peru and 224 km to the east in Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

. Estimates of its magnitude range from 8.5 to 9.0. A 600 km rupture length has been estimated from the pattern of isoseismals

Isoseismal map

In seismology an isoseismal map is used to show lines of equal felt seismic intensity, generally measured on the Modified Mercalli scale. Such maps help to identify earthquake epicenters, particularly where no instrumental records exist, such as for historical earthquakes...

 making it one of the largest fault breaks in modern times.

About 400 aftershock

Aftershock

An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...

s were recorded by 25 August of that year.

Tsunami

Although this event generated a tsunami that was noted across the Pacific, most of the associated damage was localised along the coasts of southern Peru and what is now northernmost Chile. The first wave arrived at Arica 52 minutes after the earthquake, with a 12 m height, followed by the largest 16 m wave 73 minutes later.

Future risk

The Arica area forms part of a seismic gap

Seismic gap

A seismic gap is a segment of an active fault that has not slipped in an unusually long time when compared with other segments along the same structure. Seismic gap hypothesis/theory states that, over long periods of time, the displacement on any segment must be equal to that experienced by all...

between 15° and 24°S, with no major earthquake after 1877. In accordance with this theory "a strong event is likely to occur in the near future". An earthquake affecting the same sector of the plate boundary as the 1868 event with a magnitude of 8.6 has been forecast as likely to occur by 2010. A repeat of the 1868 event would probably cause more casualties, because of the increase of population in areas at risk.