1976 Guatemala earthquake
Encyclopedia
The 1976 Guatemala earthquake struck on February 4, 1976 at 03:01:43 local time (09:01:43 UTC-6
UTC-6
UTC−06 is an identifier for a time offset from UTC of −06. This time is used in:-Central America:*Belize*Costa Rica*El Salvador*Guatemala*Honduras*Nicaragua-Central Standard Time:...

). It was a 7.5 Mw
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

 earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

, centered in the Motagua Fault
Motagua Fault
The Motagua Fault is a major, active left lateral-moving transform fault which cuts across Guatemala. It forms part of the tectonic boundary between the North American Plate and the Caribbean Plate...

, about 160 km northeast of Guatemala City
Guatemala City
Guatemala City , is the capital and largest city of the Republic of Guatemala and Central America...

, Guatemala
Guatemala
Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...

. The quake's hypocenter was located at a depth of 5 km near the town of Los Amates
Los Amates
Los Amates is a municipality in the Izabal department of Guatemala. Their population is about 56,000. Their mayor is currently Marco Tulio Ramirez Estrada.Los Amates is located on the Motagua River, from the ruins of the ancient Maya city of Quiriguá....

 in the department of Izabal
Izabal
Izabal may refer to various locations in Guatemala:* Izabal Department* Lago de Izabal a lake within Izabal department* Izabal a town within Izabal department...

.

Cities throughout the country suffered damage, and most adobe
Adobe
Adobe is a natural building material made from sand, clay, water, and some kind of fibrous or organic material , which the builders shape into bricks using frames and dry in the sun. Adobe buildings are similar to cob and mudbrick buildings. Adobe structures are extremely durable, and account for...

 type houses in the outlying areas of Guatemala City were completely destroyed. The earthquake struck during the early morning (at 3:01 am, local time) when most people were asleep. This contributed to the high death toll of 23,000. Approximately 76,000 were injured, and many thousands left homeless. Some of areas went without electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 and communications for days.

The main shock was followed by thousands of aftershock
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...

s, some of the larger ones causing additional damage and loss of life.

Seismic data

The quake's epicentre was located near the town of Los Amates
Los Amates
Los Amates is a municipality in the Izabal department of Guatemala. Their population is about 56,000. Their mayor is currently Marco Tulio Ramirez Estrada.Los Amates is located on the Motagua River, from the ruins of the ancient Maya city of Quiriguá....

, in the eastern part of the Motagua Fault
Motagua Fault
The Motagua Fault is a major, active left lateral-moving transform fault which cuts across Guatemala. It forms part of the tectonic boundary between the North American Plate and the Caribbean Plate...

, a left-lateral strike-slip fault that forms the tectonic boundary between the North American plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...

 and the Caribbean plate
Caribbean Plate
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America....

. Ground shaking was felt during approximately 39 seconds, and caused visible rupturing over 230 km along the Motagua fault, while the inferred length of faulting—based on aftershock registration—was estimated at 300 km. Average horizontal displacement along the Motagua fault was 100 cm, with a maximum displacement of 326 cm.

Maximum seismic intensity (MM
Mercalli intensity scale
The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...

 IX) was located in the Mixco
Mixco
Mixco is a municipality in the Guatemala department of Guatemala.Located next to the main Guatemala City municipality, over time it has become part of the Guatemala City Metropolitan Area. Most of Mixco is separated from the city by canyons, for which a multitude of bridges have been created. ...

 area, some sections of Guatemala City and in Gualán
Gualán
Gualán is a municipality in the Guatemalan department of Zacapa.Gualán is a small city located in the department of Zacapa in the country of Guatemala...

. A seismic intensity of MM VI covered an area of 33,000 km². Liquefaction and sand boil
Sand boil
Sand boils or Sand Volcanoes occur when water under pressure wells up through a bed of sand. The water looks like it is "boiling" up from the bed of sand, hence the name.-Flood protection structures:...

s were observed in several locations with high seismic intensity.

The main quake activated secondary fault zones, including the Mixco fault, located in a densely populated area just north-west of Guatemala City.

Several heavy aftershocks, ranging from 5.2 to 5.8 Mw caused additional casualties and hampered relief efforts.

Victims and damage

The most heavily affected area covered some 30,000 km², with a population of 2.5 million. Some 23,000 people were reported dead and 77,000 wounded. Approximately 258,000 houses were destroyed, leaving about 1.2 million people homeless. 40% of the national hospital infrastructure was destroyed, while other health facilities also suffered substantial damage.

International reaction

Very soon after the earthquake, the then president Kjell Eugenio Laugerud García
Kjell Eugenio Laugerud García
Kjell Eugenio Laugerud García was President of Guatemala from 1 July 1974 to 1 July 1978. He was the son of a Norwegian father and Guatemalan mother....

invited most of the foreign ambassadors to tour the affected regions by helicopter, which prompted them to quickly ask for help in their home countries. For example, the United States of America rebuilt most of the roads, and the Canadians and Belgians each rebuilt a village.

External links

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