An intraplate earthquake is an earthquake that occurs in the interior of a tectonic plate, in contrast to an interplate earthquake on the boundary of a tectonic plate. It is also called an intraslab earthquake, especially when occurring in a microplate.
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 earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
The 1977 San Juan earthquake, also known as Caucete earthquake, took place in the province of San Juan, Argentina, on 23 November at 06:26:26 AM. It measured 7.5 on the moment magnitude scale, and had a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale.
The 1868 Arica earthquake occurred on 13 August 1868, near Arica, then part of Peru, now part of Chile, at 21:30 UTC. It had an estimated magnitude between 8.5 and 9.3. A tsunami in the Pacific Ocean was produced by the earthquake, which was recorded in Hawaii, Japan, Australia, and New Zealand.
The 1935 Sumatra earthquake occurred at on 28 December. It had a magnitude of 7.7 and a maximum felt intensity of VII (Damaging) on the European macroseismic scale. It triggered a minor tsunami.
The 1877 Iquique earthquake occurred at 21:16 local time on 9 May. It had a magnitude of 8.5 on the surface-wave magnitude scale. Other estimates of its magnitude have been as high as 8.9 and 9.0 . It had a maximum intensity of XI (Extreme) on the Mercalli intensity scale and triggered a devastating tsunami. A total of 2,385 people died, mainly in Fiji from the tsunami.
The San Ramón is a Chilean geological fault, located in eastern Santiago Metropolitan Region, passing through the eastern part of Santiago marking the boundary between the Chilean Central Valley and the Andes. As an active thrust fault it constitutes a seismic hazard zone for the densely populated Santiago. A large number of homes and educational centers have been built on or near the fault, along with a gas plant in Peñalolén. The Chilean Nuclear Energy Commission has a reactor in La Reina, very close to the fault, which has raised concerns among the population. It runs 5 kilometers underground and extends for 25 kilometers in a north–south direction, lying between the Mapocho River and Maipo River. It is known to pass underneath the communes of Vitacura, Las Condes, La Reina, Peñalolén, La Florida and Puente Alto, and suspected to continue into Lo Barnechea and Pirque at its extremes. Due to its shallowness, it can cause very destructive superficial earthquakes with a magnitude around 7 on the Richter scale, with a general recurrence period of over 300 years.
The 2010 Pichilemu earthquakes, also known as the Libertador O'Higgins earthquakes, were a pair of intraplate earthquakes measuring 6.9 and 7.0 that struck Chile's O'Higgins Region on 11 March 2010 about 16 minutes apart. The earthquakes were centred 15 kilometres (9.3 mi) northwest of the city of Pichilemu.
The 1992 Murindó earthquake occurred on October 18 at 15:11 UTC with an epicenter in the Department of Chocó, northern Colombia. The shallow magnitude 7.2 earthquake struck northwest of the town of Murindó, killing ten and injured more than a hundred. Thirty-three municipalities were severely damaged.
The 1965 Valparaíso earthquake struck near La Ligua in Valparaíso Region, Chile, about 140 km (87 mi) from the capital Santiago on Sunday, March 28 at 12:33 local time. The moment magnitude (Mw ) 7.4–7.6 earthquake killed 400–500 people and inflicted US$1 billion in damage. Many deaths were from El Cobre, a mining location that was wiped out after a series of dam failures caused by the earthquake spilled mineral waste onto the area, burying hundreds of residents. The shock was felt throughout the country and along the Atlantic coast of Argentina.
On January 30, 1973, at 15:01 (UTC–6), a magnitude 7.6 earthquake struck 35.3 km (21.9 mi) beneath the Sierra Madre del Sur range in the Mexican states of Colima, Jalisco and Michoacán. On the Mercalli intensity scale, the earthquake reached a maximum intensity of X (Extreme), causing serious damage in the region. At least 56 people were killed and about 390 were injured. The event is commonly referred to as the Colima earthquake.
The 1856 Heraklion earthquake, also known as the Crete earthquake or Rhodes earthquake, occurred on the morning of October 12 at 02:45 am local time. This extremely catastrophic earthquake had an estimated magnitude of 7.7 to 8.3 at a depth of approximately 61 to 100 km. The earthquake was felt over a very wide area extending from Sicily, Italy to the Levant and North Africa. On the Greek island of Crete, the effects of the earthquake were cataclysmic, over 500 bodies were recovered in the city of Heraklion. Shockwaves from the earthquake were felt intensely, covering all of the Ottoman Empire; present-day Turkey, Cyprus and the Middle East where damage and human losses were reported. In Malta, the Għajn Ħadid Tower—a coastal watchtower built around the year 1638—was severely damaged in the earthquake, when its upper floor collapsed. In Cairo, Egypt, the earthquake destroyed buildings, created seiches in canals, and killed several people. Off the Egyptian and Italian coasts, sailors reported feeling a seaquake.
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
The 1947 Satipo earthquake was the largest earthquake in the sub-Andean region of Peru. It occurred on November 1 at 09:58:57 local time with an epicenter in the Department of Junín. The earthquake had an estimated moment magnitude (Mw ) of 7.7 and focal depth of 20 km (12 mi). Damage was severe in the towns of Satipo and La Merced, and at least 233 people died.
The 1790 Oran earthquake occurred on 10 October, striking near the coastal city of Oran in Algeria. The earthquake had an evaluated maximum seismic intensity of VIII–X on the European macroseismic scale (EMS-98). An estimated 3,000 people died during the earthquake and accompanying tsunami. The magnitude of this earthquake has been disputed among members of the paleoseismology field, with estimates ranging from 7.5 to even as small as 5.5.
The 1950 Calama earthquake occurred near the Argentina–Chile border with an epicenter near Calama, Chile in the Atacama Desert on December 9. The event had a hypocenter depth of 113.9 km, beneath the Caichinque volcanic complex. It measured magnitude Mw 8.2 on the moment magnitude scale, making it the largest intermediate depth earthquake ever recorded on Chilean soil. One person was killed and an unspecified number of people were injured in Calama.
Between May 1990 and April 1991, an earthquake sequence occurred in the Department of San Martín, northern Peru. Three large earthquakes of magnitudes (Mw ) 6.5–6.9 occurred in the same region across 11 months, causing extensive damage. At least 189 people were killed in these earthquakes.
The 1657 Concepción earthquake occurred on March 15 at 20:00 local time off the coast of Concepción, Biobío Region in the Spanish Empire. The earthquake caused severe damage along the coast, and generated a large tsunami in the Bay of Concepción. At least 40 people were killed, the majority due to drowning from the tsunami. The town of Concepción was the hardest hit, with the earthquake and tsunami totally destroying it.
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
The 2012 Constitución earthquake was recorded on March 25, 2012, at 7:37 pm local time. It had a moment magnitude of 7.1 and its epicenter was located 23 km (14 mi) northeast of the city of Constitución, in the Maule Region, Chile. According to experts, it was a strong and late aftershock of the Great Chile earthquake of February 27, 2010.
