1980 Azores Earthquake
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Striking the Autonomous Region of the Azores on 1 January, the 1980 Azores Island earthquake killed 73 people and injured over 400, causing severe damage on the islands of
Terceira Terceira () is a volcanic island in the Azores archipelago, about a third of the way across the North Atlantic Ocean at a similar latitude to Portugal's capital Lisbon, with the island group forming an insular part of Portugal. It is one of the ...
and São Jorge. Resulting from a strike slip fracture, typical of other historical Azorean earthquakes, and measuring 6.9 on the
moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mwg, 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. was defined in a 1979 paper ...
, 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 Ribe ...
and Faial. In response to the earthquake, Portuguese president
António Ramalho Eanes António dos Santos Ramalho Eanes (born 25 January 1935) is a Portuguese general and politician who was the 16th president of Portugal from 1976 to 1986. Background Born at Alcains, Castelo Branco, he is the son of Manuel dos Santos 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 commonly defined as a vent or fissure 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 fo ...
in origin, the Azores lie in a
tectonically Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons. These processes ...
complex area on either side of the
Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountai ...
, between the
European European, or Europeans, may refer to: In general * ''European'', an adjective referring to something of, from, or related to Europe ** Ethnic groups in Europe ** Demographics of Europe ** European cuisine, the cuisines of Europe and other West ...
,
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
and African plate boundaries, forming their own
microplate A microplate, also known as a microtiter plate, microwell plate or multiwell, is a flat plate with multiple "wells" used as small test tubes. The microplate has become a standard tool in analytical research and clinical diagnostic testing lab ...
.Borges et al. (2007), p.37–54 The 1980 earthquake was the result of movement along a northwest to southeast trending
strike-slip fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
. After
aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), crust adjusts to the effects of the main shock. Large earthq ...
s from the quake had concluded, a study took place, identifying focal solutions for these small events. The type of faulting responsible for 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 (depending upon dialect, a sheep may be sai ...
in the right-lateral (
dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...
) direction. All faulting in this area is
strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
-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, about a third of the way across the North Atlantic Ocean at a similar latitude to Portugal's capital Lisbon, with the island group forming an insular part of Portugal. It is one of the ...
,
São Jorge Island São Jorge (; Portuguese language, Portuguese for 'Saint George') 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 Island, Pico and Faial Isl ...
, and
Graciosa Graciosa Island () (literally "graceful" or "enchanting" in Portuguese), also referred to as the ''White Island'', is a volcanic island in the Atlantic Ocean. It is the northernmost of the Central Group of islands in the Azores archipelago. The o ...
), 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 Angra do Heroísmo (), or simply Angra, is a city and municipality on Terceira Island, Portugal, and one of the three capital cities of the Azores. Founded in 1478, Angra was historically the most important city in the Azores, as seat of the Roma ...
. 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 r ...
such as electricity and water, were reported cut in several areas. Initially, the number of fatalities was set at 52. It was later revised to 61 and finally to 72. 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 (; ), officially designated Air Base No. 4 (''Base Aérea N.º 4'', BA4) , is a multi-use airfield near Lajes and northeast of Angra do Heroísmo on Terceira Island in the Azores, Portugal. It is home to the Port ...
air base, nor any major damage.


Relief efforts and response

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
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 army aviati ...
personnel stationed at Lajes functioned as disaster relief workers, sheltering as many as 150 families.
Portuguese Air Force The Portuguese Air Force () is the air force, aerial warfare force of Portugal. Locally it is referred to by the acronym FAP but internationally is often referred to by the acronym PRTAF. It is the youngest of the three branches of the Portuguese ...
members brought supplies to earthquake victims, while a
Portuguese Navy The Portuguese Navy (), also known as the Portuguese War Navy (''Marinha de Guerra Portuguesa'') or as the Portuguese Armada (''Armada Portuguesa''), is the navy of the Portuguese Armed Forces. Chartered in 1317 by King Dinis of Portugal, it is ...
transported medical officials to the island. The Portuguese president,
António Ramalho Eanes António dos Santos Ramalho Eanes (born 25 January 1935) is a Portuguese general and politician who was the 16th president of Portugal from 1976 to 1986. Background Born at Alcains, Castelo Branco, he is the son of Manuel dos Santos 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) was 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
seismograph A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The out ...
ic 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 Geothermal is related to energy and may refer to: * Geothermal energy, useful energy generated and stored in the Earth * Geothermal activity, the range of natural phenomena at or near the surface, associated with release of the Earth's internal he ...
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
landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...
s remain.


See also

* List of earthquakes in 1980 * List of earthquakes in Portugal * List of earthquakes in the Azores


References

; Notes ; Sources * * * * * * *


External links

* {{Earthquakes in 1980 Azores Islands Earthquake, 1980 Azores Islands Earthquake, 1980 Earthquakes in Portugal January 1980 in Europe Strike-slip earthquakes