|UTC time||1982-06-19 06:21:58|
|Local date||19 June 1982|
|Duration||25 s (shaking felt)|
|Depth||82 km (51 mi)|
|Areas affected||El Salvador|
|Total damage||$5 million|
|Max. intensity||VII (Very strong)|
The 1982 El Salvador earthquake occurred southeast of San Salvador on 19 June at 00:21 local time (06:21 UTC). This undersea earthquake struck offshore in the Pacific Ocean and had a surface wave magnitude of 7.2 and a maximum Mercalli intensity of VII (Very strong). Occurring adjacent to a subduction zone at the Middle America Trench, this normal-slip shock left at least 16 and as many as 43 people dead, and many injured, and also inflicted $5 million in damage.
San Salvador is the capital and the most populous city of El Salvador and its eponymous department. It is the country's political, cultural, educational and financial center. The Metropolitan Area of San Salvador which comprises the capital itself and 13 of its municipalities has a population of 2,404,097.
The Middle America Trench is a major subduction zone, an oceanic trench in the eastern Pacific Ocean off the southwestern coast of Middle America, stretching from central Mexico to Costa Rica. The trench is 1,700 miles (2,750 km) long and is 21,880 feet at its deepest point. The trench is the boundary between the Rivera, Cocos, and Nazca plates on one side and the North American and Caribbean plates on the other. It is the 18th-deepest trench in the world. Many large earthquakes have occurred in the area of the Middle America Trench.
Near the Salvadorian coast, the Cocos Plate is subducting beneath the Caribbean Plate at the Middle America Trench. This earthquake was an intra-slab, normal-slip subduction earthquake in the subducting plate. The subduction zone and a local system of faults along the volcanic chain are two major sources of the earthquakes in El Salvador.
The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate broke into two pieces, which also created the Nazca Plate. The Cocos Plate also broke into two pieces, creating the small Rivera Plate. The Cocos Plate is bounded by several different plates. To the northeast it is bounded by the North American Plate and the Caribbean Plate. To the west it is bounded by the Pacific Plate and to the south by the Nazca Plate.
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.
The mechanism of this earthquake had many similarities with the El Salvador earthquake of 13 January 2001.
The intensity in San Salvador reached VII (Very strong).The most affected cities are San Salvador, Ahuachapán, Concepción de Ataco, Comasagua, San Miguel, San Pedro Nonualco, and San Juan Tepezontes. This earthquake could be felt in Guatemala, Honduras, Nicaragua, and Costa Rica, with intensities V (Moderate) in Guatemala City, Guatemala, IV (Light) in Tegucigalpa, Honduras, V in Managua, Nicaragua, and III (Weak) in San José, Costa Rica.
Ahuachapán is a city and municipality and the capital of the Ahuachapán Department in western El Salvador. The municipality including the city covers an area of 244.84 km² and as of 2007 has a population of 110,511 people. Situated near the Guatemalan border, it is the westernmost city in the country and is the center of an agricultural region producing primarily coffee.
Concepción de Ataco is a municipality and city within the Ahuachapán Department, El Salvador. It has an area of 61.03 km ² and a population of 18,101 inhabitants.
San Miguel is a city in eastern El Salvador. It is the country's third most populous city.. It is located 138 km east of the capital, San Salvador. It is also the capital of the department of San Miguel and a municipality. The population of the city in 2017 was 518,410.
Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle. Regions where this process occurs are known as subduction zones. Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries.
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 are the most powerful earthquakes.
Comasagua is a municipality in the La Libertad department of El Salvador.
A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most slow earthquakes now appear to be accompanied by fluid flow and related tremor, which can be detected and approximately located using seismometer data filtered appropriately. That is, they are quiet compared to a regular earthquake, but not "silent" as described in the past.
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Episodic tremor and slip (ETS) is a seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface. Slow slip events are distinguished from earthquakes by their propagation speed and focus. In slow slip events, there is an apparent reversal of crustal motion, although the fault motion remains consistent with the direction of subduction. ETS events themselves are imperceptible to human beings and do not cause damage.
The 1717 Guatemala earthquake struck 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 1965 Puget Sound earthquake occurred at 08:28 PDT on April 29 within the Puget Sound region of Washington State. It had a magnitude of 6.7 on the moment magnitude scale and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. It caused the deaths of seven people and about $12.5–28 million in damage. There were no recorded aftershocks.
The 1773 Guatemala earthquake struck Guatemala on July 29 at 15:45 local time. It had an estimated epicentral magnitude of 7.5 Mi. It was part of a sequence that started in May that year. There were two strong foreshocks on June 11 and the mainshock was followed by numerous aftershocks which lasted until December 1773. The series of all these earthquakes is also referred to as the Santa Marta earthquake(s) as it had started on the feast day of Saint Martha.
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