An interplate earthquake is an earthquake that occurs at the boundary between two tectonic plates. Earthquakes of this type account for more than 90 percent of the total seismic energy released around the world. If one plate is trying to move past the other, they will be locked until sufficient stress builds up to cause the plates to slip relative to each other. The slipping process creates an earthquake with relative displacement on either side of the fault, resulting in seismic waves which travel through the Earth and along the Earth's surface. Relative plate motion can be lateral as along a transform fault boundary, vertical if along a convergent boundary or a divergent boundary, and oblique, with horizontal and lateral components at the boundary. Interplate earthquakes associated at a subduction boundary are called megathrust earthquakes, which include most of the Earth's largest earthquakes.
The 1957 Andreanof Islands earthquake occurred at 04:22 local time on March 9 with a moment magnitude estimated between 8.6 and 9.1 and a maximum Modified Mercalli intensity of VIII (Severe). It occurred south of the Andreanof Islands group, which is part of the Aleutian Islands arc. The event occurred along the Aleutian Trench, the convergent plate boundary that separates the Pacific Plate and the North American plates near Alaska. A basin-wide tsunami followed, with effects felt in Alaska and Hawaii, and strong waves recorded across the Pacific rim. Total losses were around $5 million.
The January 2001 El Salvador earthquake struck El Salvador on January 13, 2001, at 17:33:34 UTC. The 7.6 quake struck with the epicenter 60 miles (100 km) SW of San Miguel, El Salvador at a depth of 60 km.
The 1902 Guatemala earthquake occurred on April 18 at 8:23 pm with a moment magnitude of 7.5 and a maximum Mercalli intensity of VIII (Severe). The rupture was initiated at a depth of 25 km (16 mi) and the duration was 1 to 2 minutes.
The 1717 Guatemala earthquake struck colonial Guatemala on September 29 with an estimated moment magnitude of 7.4, and a Mercalli intensity of approximately IX (Violent). The earthquake essentially destroyed much of the architecture of Antigua Guatemala, which was the colonial capital of Central America at the time. Over 3,000 buildings were ruined including many temples and churches. Such was the effect of the disaster that the authorities considered moving the headquarters to a settlement which was less prone to natural disasters.
The 1995 Colima–Jalisco earthquake occurred on October 9 at 15:35 UTC with a moment magnitude of 8.0 and a maximum Mercalli intensity of VIII (Severe). The shock occurred off the coast of Jalisco, Mexico, where a tsunami was triggered that affected a 200 km (120 mi) stretch of the coast. The earthquake could be felt in Mexico City and in high-rise buildings in Dallas and Houston. In Mexico, the Cihuatlan-Manzanillo was the most severely affected area. At least 49 people died and 100 were injured.
The 1965 Oaxaca earthquake occurred in Mexico on August 23 at with a moment magnitude of 7.5. Five people were reported dead in Mexico City and one in Oaxaca. There was an anomalous change in seismic activities before the earthquake. There was a quiescent stage from late 1963 to mid-1964, and it was followed by a renewal of seismic activities before the main shock. This earthquake was a shallow thrust earthquake in the interplate subduction zone, in which the Cocos Plate is subducting beneath the North American Plate.
The 1994 offshore Sanriku earthquake occurred on December 28, 1994, at 12:19 UTC. This was a magnitude 7.7 earthquake with epicenter located in the Pacific Ocean at about 180 km east of Hachinohe, Aomori. The intensity reached shindo 6 in Hachinohe, Aomori, about 187.6 km from epicenter. It could be felt in Tokyo, about 632.9 km from epicenter, with shindo 2. The Japanese Meteorological Agency put the magnitude at 7.5. Slip associated with this earthquake continued for more than a year and it has been termed an 'ultra-slow earthquake'.
The 1953 Tumbes earthquake occurred on December 12 at near the border between Peru and Ecuador. The shock had a moment magnitude of 7.5, a maximum Mercalli Intensity of VIII (Severe), and occurred in the northwestern offshore area of Tumbes, Peru.
The 1942 Guatemala earthquake occurred at on August 6 and had ratings of 7.7 on the moment magnitude scale and 7.9 on the surface wave magnitude scale. The epicenter was located off the southern coast of Guatemala, and it was one of the strongest earthquakes ever recorded there.
The 1979 Tumaco earthquake occurred at on 12 December with a moment magnitude of 8.2 and a maximum Mercalli intensity of IX (Violent). The epicenter was just offshore from the border between Ecuador and Colombia, near the port city of Tumaco. It triggered a major tsunami, which was responsible for most of the estimated 300–600 deaths. The hardest hit area was Colombia's Nariño Department.
The 1942 Peru earthquake occurred on August 24 at and was located near the border of the departments of Ica and Arequipa, Peru. It had a magnitude of 8.2 or 8.4.
The February 2001 El Salvador earthquake occurred with a moment magnitude of 6.6 on 13 February at 14:22:05 UTC. The epicentre was 15 miles (30 km) E of San Salvador, El Salvador, at a depth of 10 km. At least 315 people were killed, 3,399 were injured, and extensive damage affected the area. Another 16,752 homes were damaged and 44,759 destroyed. The most severe damage occurred in the San Juan Tepezontes-San Vicente-Cojutepeque area, though it was felt throughout the country and in neighboring Guatemala and Honduras. Landslides occurred in many areas of El Salvador.
An earthquake occurred on 26 August 2012 at 22:37 local time. The earthquake located off the coast of El Salvador measured 7.3 on the moment magnitude scale and had a focal depth of 16.0 kilometres (10 mi). No deaths were reported, however more than 40 people were injured when they were caught in a tsunami generated by the earthquake. Waves from the tsunami were unusually large for an earthquake of this size. The large waves were attributed to the earthquake's unique rupture characteristic. In addition to the absence of fatalities, damage caused by the earthquake and tsunami was minimal as a result of the sparse population around the affected region and the slow rupture characteristic of the event.
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 1965 San Salvador earthquake occurred at 04:01 in the morning on May 3, 1965. It had a moment magnitude of 5.9 and a maximum Mercalli intensity of VIII (Severe). The shock caused severe damage to El Salvador's capital city, San Salvador. The town of Ilopango, Soyapango, and Delgado was also hard hit. The earthquake was the most destructive to affect the city prior to the 1986 earthquake.
The 1959 Coatzacoalcos earthquake occurred at 02:25 local time on August 26 near the Mexican state of Veracruz. The earthquake measured 6.4 Mw at a depth of 21 km (13 mi), and had a maximum Modified Mercalli intensity of VIII (Severe). It had an epicenter immediately off the coast of Coatzacoalcos. The shallow back-arc thrust faulting earthquake damaged the cities of Acayucan, Coatzacoalcos, Jáltipan and Minatitlán. A total of 25 people died, including 10 from Jáltipan while a further 200 were injured. The Middle America Trench, a subduction zone that borders the southwestern coast of Mexico and Central America, accounts for much of the seismicity in Mexico. The eastern side of the country near the Gulf of Mexico rarely experiences large earthquakes although they have been recorded around the Veracruz area, where seismicity is higher compared to other parts of the gulf. Seismicity in the gulf is attributed to back-arc compression due to subduction.
The 1917 San Salvador earthquake occurred on June 7 at 18:55 local time near the Salvadoran capital. The hypocenter of the Mw 6.7 was at a shallow depth of 15 km (9.3 mi), and occurred along a shallow crustal fault near San Salvador. The earthquake caused significant destruction of the city and left approximately 1,050 dead. It was followed by an eruption on San Salvador that killed another 1,100. Only behind the earthquake of 1986, it is the second deadliest in El Salvador's history.
