1980 Azores Islands earthquake
Encyclopedia
Striking the Autonomous Region of Azores on January 1, the 1980 Azores Island earthquake killed 61 people and injured over 400, causing severe damage on the islands of Terceira
and São Jorge. Measuring 7.2 on the Richter scale, it also shook the islands of Pico
and Faial
. The earthquake was found to be, like other Azores earthquakes, ruptured in a strike slip motion.
In response to the earthquake, Portuguese president António Ramalho Eanes
announced three days of national mourning. Relief efforts, initiated by local Air Force agents, were successful and were soon accompanied by government-supported agencies.
in origin and lie in a tectonically
complex area to the east of the Mid-Atlantic Ridge
. They lie close to the boundary between the Eurasian
and African plate
but are generally considered to form their own microplate. The 1980 earthquake was caused by movement on a northwest-southeast trending strike-slip fault.
After aftershock
s from the quake had concluded, examination took place, producing a focal solution
to the small events. Movement of these shocks were similar to previous earthquakes around the Azores Islands. For these earthquakes, scientists had determined that the conjugate nodal
plane was responsible, seeing fault shear 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.
. In general, public buildings such as churches remained, in spite of several that caved in on themselves. Public utilities
such as electricity and water, were reported cut in several areas.
Initial fatality numbers were set at 52, this was later revised to 61. Additionally, the injuries were set at 300 but this was 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
air base, nor any major damage.
navy ship transported medical officials to the island. The 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 transportation. Responding to the situation, they were to look through rubble spawned from the earthquake for survivors. Soon after, huts were built to replace the destroyed homes for 200 families of the islands. 100 huts were constructed by a People to People
project fund.
Three days of national mourning were declared by Eanes. Nineteen seismograph stations have since been installed and are relied on by most of the islands' people. Eleven of them are used to monitor activity, while the other eight also record information on a geothermal
area.
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.
The area around the Azores remains active. Threats from earthquakes and landslide
s remain.
Terceira Island
Referred to as the “Ilha Lilás” , Terceira is an 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 56,000 inhabitants in an area of approximately 396.75 km²...
and São Jorge. Measuring 7.2 on the Richter scale, it also shook the islands of Pico
Pico Island
Pico Island , is an island in the Central Group of the Portuguese Azores noted for its eponymous volcano, Ponta do Pico, which is the highest mountain in Portugal, the Azores, and the highest elevation of the Mid-Atlantic Ridge...
and Faial
Faial Island
Faial Island , also known in English as Fayal, is a Portuguese island of the Central Group of the Azores....
. The earthquake was found to be, like other Azores earthquakes, ruptured in a strike slip motion.
In response to the earthquake, Portuguese president António Ramalho Eanes
António Ramalho Eanes
António dos Santos Ramalho Eanes, GColTE, GCL, CavA, KE is a Portuguese general and politician who was the 16th President of Portugal from 1976 to 1986.-Background:...
announced three days of national mourning. Relief efforts, initiated by local Air Force agents, were successful and were soon accompanied by government-supported agencies.
Background
In 1950, another strong earthquake had rocked the Azores Islands region, and this was the largest earthquake since.Description
The Azores islands are volcanicVolcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....
in origin and lie in a tectonically
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
complex area to the east of the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
. They lie close to the boundary between the Eurasian
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
and African plate
African Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...
but are generally considered to form their own microplate. The 1980 earthquake was caused by movement on a northwest-southeast trending strike-slip fault.
After 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 from the quake had concluded, examination took place, producing a focal solution
Focal mechanism
The focal mechanism of an earthquake describes the inelastic deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is also known as a fault-plane solution...
to the small events. Movement of these shocks were similar to previous earthquakes around the Azores Islands. For these earthquakes, scientists had determined that the conjugate nodal
Nodal
Nodal can refer to* Nodal, a protein encoded by the gene NODAL and responsible for left-right asymmetry* Nodal , a novel music composition program...
plane was responsible, seeing fault shear 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 struck the Azores Islands with a Richter scale magnitude of 7.2. Causing considerable damage on three separate islands (Terceira, São Jorge, and Graciosa), it destroyed several buildings. According to local reports, roughly 70 % of the houses on Terceira were completely demolished, including the historic quarter of the-then island capital, Angra do HeroísmoAngra do Heroísmo
Angra do Heroísmo , locally referred to as Angra, is a municipality and city on the island of Terceira, within the Portuguese autonomous region of the Azores. The municipal area has a population of 35,581 and an area of . Along with Praia da Vitória to the north, it is one of two municipal...
. In general, public buildings such as churches remained, in spite of several that caved in on themselves. Public utilities
Public utility
A public utility is an organization that maintains the infrastructure for a public service . Public utilities are subject to forms of public control and regulation ranging from local community-based groups to state-wide government monopolies...
such as electricity and water, were reported cut in several areas.
Initial fatality numbers were set at 52, this was later revised to 61. Additionally, the injuries were set at 300 but this was 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
Lajes Field or Lajes Air Base , officially designated Air Base No. 4 , is a multi-use air field, home to the Portuguese Air Force Base Aérea Nº4 and Azores Air Zone Command , a United States Air Force detachment , and a regional air passenger terminal located near Lajes...
air base, nor any major damage.
Relief efforts and response
United States Navy and Air Force troops 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 João Coutinho class corvetteJoão Coutinho class corvette
The João Coutinho class corvettes were a series of corvettes built for the Portuguese Navy for service in Portugal's African colonies. The corvettes were designed in Portugal by naval engineer Rogério de Oliveira, but the urgent need of their services in the Portuguese Colonial War meant that the...
navy ship transported medical officials to the island. The President António Ramalho Eanes
António Ramalho Eanes
António dos Santos Ramalho Eanes, GColTE, GCL, CavA, KE is a Portuguese general and politician who was the 16th President of Portugal from 1976 to 1986.-Background:...
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 transportation. Responding to the situation, they were to look through rubble spawned from the earthquake for survivors. Soon after, huts were built to replace the destroyed homes for 200 families of the islands. 100 huts were constructed by a People to People
People to People International
People to People International was established on September 11, 1956, by President Dwight D. Eisenhower, as part of the U.S. Information Agency...
project fund.
Three days of national mourning were declared by Eanes. Nineteen seismograph stations have since been installed and are relied on by most of the islands' people. Eleven of them are used to monitor activity, while the other eight also record information on a geothermal
Geothermal
Geothermal is related to energy and may refer to:* The geothermal gradient and associated heat flows from within the Earth- Renewable technology :...
area.
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 or had not been adequately addressed.The area around the Azores remains active. Threats from earthquakes and landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
s remain.