The 1992 Nicaragua earthquake occurred off the coast of

Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the countr ...

at 6:16 p.m. on 1 September. Some damage was also reported in Costa Rica. At least 116 people were killed and several more were injured. The earthquake was caused by movement on a convergent plate boundary. It created a

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

disproportionately large for its surface wave magnitude.

Tectonic setting

Nicaragua lies above the convergent boundary where the Cocos Plate is being subducted beneath the Caribbean Plate. The convergence rate across this boundary is about 73 mm per year. There have been many large earthquakes in this part of the plate boundary, including events in 1982, 2001, 2012 ( El Salvador, Costa Rica and Guatemala) and

2014 File:2014 Events Collage.png, From top left, clockwise: Stocking up supplies and personal protective equipment (PPE) for the Western African Ebola virus epidemic; Citizens examining the ruins after the Chibok schoolgirls kidnapping; Bundles of wat ...

. The 2001 and 2014 events were a result of normal faulting within the subducting Cocos Plate, with the others representing faulting along the plate interface.

Earthquake

This event was the first

tsunami earthquake In seismology, a tsunami earthquake is an earthquake which triggers a tsunami of significantly greater magnitude, as measured by shorter-period seismic waves. The term was introduced by Japanese seismologist Hiroo Kanamori in 1972. Such events a ...

to be recorded using modern broadband instruments. The initial surface wave magnitude, which uses only waves of a period of 20 seconds, was estimated at 7.0–7.2. The part of the Middle America Trench off Nicaragua contains relatively little sediment, allowing the slip to propagate up- dip all the way to the trench bottom, which tends to generate large tsunamis. The trench sediment here has been subducted and this soft material lies along the plate interface. The rupture speed along such a zone is significantly slower than for most subduction zone thrust earthquakes, while the

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of the earthquake was much shallower than the typical subduction zone earthquake. Using longer period seismic waves, magnitudes have been calculated in the range 7.6–7.7 M_w, consistent with the size of the observed tsunami.

Damage and casualties

The first shock of the earthquake occurred at 00:16

GMT Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a cons ...

and was followed by several strong aftershocks.Nicaragua Earthquake/Tsunami Situation Reports 1–7

United Nations Department of Humanitarian Affairs The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) is a United Nations (UN) body established in December 1991 by the General Assembly to strengthen the international response to complex emergencies and natural disaster ...

The quake was most widely felt in the Chinandega and León

departments of Nicaragua __NOTOC__ Nicaragua is a unitary republic, divided for administrative purposes into fifteen departments (Spanish: ) and two autonomous regions (Spanish: ): Autonomous regions In 1987, the new constitution established the Charter of Autonom ...

, though it was also felt elsewhere in Nicaragua at

El Crucero El Crucero () is a municipality in the Managua department of Nicaragua. It is located on the summit and slopes of the ''Sierras de Managua'', east of Jinotepe Jinotepe () is a city and municipality in the Carazo department of Nicaragua. I ...

Managua ) , settlement_type = Capital city , motto = , image_map = , mapsize = , map_caption = , pushpin_map = Nicar ...

and San Marcos and at San José in Costa Rica. It was the strongest seismic event to hit Nicaragua since the earthquake of 1972. At least 116 people were killed, most being children sleeping in their beds, with more than 68 missing and over 13,500 left homeless in Nicaragua. At least 1,300 houses and 185 fishing boats were destroyed along the west coast of Nicaragua. Total damage in Nicaragua was estimated at between 20 and 30 million U.S. dollars. According to the Augusto César Sandino Foundation, the most affected were "inhabitants of small poor communities who live from diverse subsistence activities. Their houses, located beside the sea, were almost entirely destroyed. These people have lost their livelihoods, poor peasants who grow basic grains for their own consumption in marginal areas, and fisherpeople who have lost their fishing equipment, boats, storage sheds and warehouses. Their already extreme poverty has been exacerbated."

Tsunami

Most of the casualties and damage were caused by a tsunami affecting the west coasts of Nicaragua and Costa Rica, and it was one of three tsunamis to occur within a span of six months. Runup heights were measured shortly after the earthquake and reached heights of up to 9.9 meters, though the average height was 3 to 8 meters. The

was disproportionately large for its surface wave magnitude, or , and the duration of the rupture process was 100 s, unusually long for its size. The

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

was 7.6, larger than the 20-second M_s of 7; this M_s–M_w difference is a characteristic of tsunami earthquakes. Tide gauges were set up at Corinto and Puerto Sandino, which showed an impulsive tsunami originating 61 minutes after the earthquake. It ran inland 1,000 meters to Masachapa, the hardest hit major town of all, with nine fatalities.

Relief efforts

From the onset of the disaster, authorities provided initial assistance. President

Violeta Chamorro Violeta Barrios Torres de Chamorro (; 18 October 1929) is a Nicaraguan politician who served as President of Nicaragua from 1990 to 1997. She was the first and, as of 2022, only woman to hold the position of president of Nicaragua. Born into ...

stated in her speech to the nation on 2 September 1992, that no international assistance was needed. However, the

Red Cross The International Red Cross and Red Crescent Movement is a humanitarian movement with approximately 97 million volunteers, members and staff worldwide. It was founded to protect human life and health, to ensure respect for all human beings, and ...

did assist in some operations while the National Civil Defence carried out much of the relief operations, with wounded people being transported to the Hospital Leon and Lenin-Fonseca Hospital.

References

External links

Nicaragua Earthquake/Tsunami Sep 1992 UNDHA Situation Reports 1–7
– UN Department of Humanitarian Affairs
M 7.7 – near the coast of Nicaragua
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

* {{Earthquakes in 1992

Earthquakes in Nicaragua 1992 tsunamis 1992 in Nicaragua September 1992 events in North America Tsunami earthquakes