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1868 Arica earthquake
The 1868 Arica earthquake was an earthquake that occurred on August 13, 1868, near Arica, then part of Peru, at 21:30 UTC. It had an estimated magnitude between 8.5 and 9.0. A tsunami (or multiple tsunamis) in the Pacific Ocean was produced by the earthquake, which was recorded in Hawaii, Japan and New Zealand.
Tectonic setting
The earthquake occurred along the boundary between the Nazca Plate and the South American Plate. The earthquake is likely to be a result of thrust-faulting, caused by the subduction of the Nazca plate beneath the South American plate.
The coastal parts of Peru and Chile have a history of great megathrust earthquakes originating from this plate boundary, such as the 1960 Valdivia earthquake.
Damage
The earthquake caused the almost complete destruction of Arica, Tacna, Moquegua, Mollendo, Ilo, Iquique, Torata and Arequipa, 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 America, the U.S. gunboat Wateree and the U.S. store ship Fredonia, which was completely destroyed in the process. The tsunami also caused the near complete destruction of the port city of Pisco.
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 and the Banks peninsula with many houses washed away and boats damaged, but only one death was recorded.
Characteristics
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, Peru and 224 km to the east in Bolivia. Estimates of its magnitude range from 8.5 to 9.0. A 600 km rupture length has been estimated from the pattern of isoseismals making it one of the largest fault breaks in modern times.
About 400 aftershocks 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 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 between 15 and 24S, 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.
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article 1868 Arica earthquake
