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Striking the Autonomous Region of Azores on 1 January, the 1980 Azores Island earthquake killed 61 people and injured over 400, causing severe damage on the islands of
Terceira Terceira () is a volcanic island in the Azores archipelago, in the middle of the North Atlantic Ocean. It is one of the larger islands of the archipelago, with a population of 53,311 inhabitants in an area of approximately . It is the location ...
and São Jorge. Measuring 6.9 on the
moment magnitude scale 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 ...
, it also shook the islands of
Pico Pico may refer to: Places The Moon * Mons Pico, a lunar mountain in the northern part of the Mare Imbrium basin Portugal * Pico, a civil parish in the municipality of Vila Verde * Pico da Pedra, a civil parish in the municipality of Ribeir ...
and Faial, and resulted from a strike slip fracture, typical of other historical Azorean earthquakes. In response to the earthquake, Portuguese president António Ramalho Eanes announced three days of national mourning, while relief efforts, initiated by agents of the local Air Force, were soon accompanied by government-supported agencies.


Geology


Background

In 1950, another strong earthquake had rocked the Azores Islands region, and this was the largest earthquake since.Western Newspapers (2 January 1980)


Description

Volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
in origin, the Azores lie in a
tectonically Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...
complex area on either side of the
Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North ...
, between the European, American and African plate boundaries, forming their own
microplate A microplate, also known as a microtiter plate (''Microtiter'' is a registered trademark in the United States, therefore it should not be used generically without attribution), microwell plate or multiwell, is a flat plate with multiple "wells" ...
.Borges et al. (2007), p.37–54 The 1980 earthquake was the result of movement along the northwest to southeast trending strike-slip fault. After aftershocks from the quake had concluded, examination took place, producing a focal solution to the small events. Movement of these shocks was similar to that of previous earthquakes around the Azores. For these earthquakes, scientists had determined that the conjugate nodal plane was responsible, seeing
shearing Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (a sheep may be said to have been "shorn" or ...
on the right-lateral ( dextral) side. All faulting in this area is strike-slip-oriented, and on a rather large scale. Because of this research, information now points towards Azores volcanism being controlled by earthquake movement.


Damage and casualties

The earthquake that struck the Azorean islands was 6.9 . It caused considerable damage on three separate islands (
Terceira Terceira () is a volcanic island in the Azores archipelago, in the middle of the North Atlantic Ocean. It is one of the larger islands of the archipelago, with a population of 53,311 inhabitants in an area of approximately . It is the location ...
,
São Jorge Island São Jorge () is an island in the central group of the Azores archipelago and part of the autonomous region of Portugal. Separated from its nearest neighbours ( Pico and Faial islands) by the Pico-São Jorge Channel, the central group is oft ...
, and
Graciosa Graciosa Island () (literally "graceful" or "enchanting" in Portuguese) is referred to as the ''White Island'', the northernmost of the Central Group of islands in the Azores. The ovular Portuguese island has an area of , a length of and a width ...
), destroying several buildings. According to local reports, roughly 70% of the houses on Terceira were completely demolished, including the historic quarter of the island capital, Angra do Heroísmo. In general, public buildings such as churches remained intact, while several buildings caved in on themselves.
Public utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and ...
such as electricity and water, were reported cut in several areas. Initially, the number of fatalities was set at 52, but it was later revised to 61. Additionally, the injuries were set at 300, but this was also revised to more than 400. At least 20,000 people were left homeless. Minor damage was recorded at Pico and Faial islands. No fatalities were recorded at the
Lajes Field Lajes Field or Lajes Air Base (; pt, Base Aérea das Lajes), officially designated Air Base No. 4 (''Base Aérea Nº 4'', BA4) , is a multi-use airfield near Lajes and northeast of Angra do Heroísmo on Terceira Island in the Azores, Portug ...
air base, nor any major damage.


Relief efforts and response

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
and
Air Force An air force – in the broadest sense – is the national military branch that primarily conducts aerial warfare. More specifically, it is the branch of a nation's armed services that is responsible for aerial warfare as distinct from an ...
personnel stationed at Lajes functioned as disaster relief workers, sheltering as many as 150 families. Portuguese Air Force members brought supplies to earthquake victims, while a
Portuguese Navy The Portuguese Navy ( pt, Marinha Portuguesa, also known as ''Marinha de Guerra Portuguesa'' or as ''Armada Portuguesa'') is the naval branch of the Portuguese Armed Forces which, in cooperation and integrated with the other branches of the Port ...
transported medical officials to the island. The Portuguese president, António Ramalho Eanes, flew in on a plane accompanied by medical personnel and supplies (such as bedding). Local officials including policemen and volunteer firemen cleared roads for relief supplies and transports. Responding to the situation, these officials were also involved in looking for survivors in the rubble. Soon after, tents were erected to replace the destroyed or unsafe homes for approximately 200 families of the islands. Portable homes were constructed by the
People to People International People to People International (PTPI) is a program established on September 11, 1956, by President Dwight D. Eisenhower, as part of the United States Information Agency. After President Eisenhower left the office of President in 1961, he arranged ...
project fund, resulting in 100 shelters. Three days of national mourning were declared by Eanes. Following the relief efforts, 19 seismographic stations were installed to monitor seismic activities. Eleven of these were used to monitor earthquake activity, while the other eight also record information on the island's geothermal areas. The earthquake forced hundreds of people to leave the country for the United States. It occurred during a period of several major natural disasters in which many residents of the island left; in 1975, 8,000 residents left. In 1981, however, just 2,500 people left the island.


Analysis and current situation

Later studies of the events leading up to the tragedy found several factors contributing to the extent of the damage. A. Malheiro (2006) linked five major causes to damage from these earthquakes. The buildings most damaged by the earthquake were near fault lines on top of loosely packed soil. They tended to be of poor construction and did not conform to proper building code, nor had they been adequately examined. The area around the Azores remains active. Threats from earthquakes and landslides remain.


See also

*
List of earthquakes in 1980 This is a list of earthquakes in 1980. Only earthquakes of magnitude 6 or above are included, unless they result in damage and/or casualties, or are notable for some other reason. Events in remote areas will not be listed but included in statist ...
*
List of earthquakes in Portugal This list documents major earthquakes affecting Portugal. See also * List of earthquakes in the Azores References {{Europe topic, List of earthquakes in Earthquakes in Portugal Portugal Portugal, officially the Portuguese Republic ...
*
List of earthquakes in the Azores The following is a list of the prominent or destructive earthquakes occurring in the Azores, or affecting the populace of the archipelago: History 16th century * 1522 Vila Franca earthquake (22 October 1522) * 1591 Vila Franca earthquake (26 Ju ...


References

; Notes ; Sources * * * * * * *


External links

* {{Earthquakes in 1980 Azores Islands Earthquake, 1980 Azores Islands Earthquake, 1980 Earthquakes in Portugal January 1980 events in Europe