1980 Azores Islands earthquake

Geology

Background

In 1950, another strong earthquake had rocked the Azores Islands region, and this was the largest earthquake since.

Description

Volcanic in origin, the Azores lie in a tectonically complex area on either side of the Mid-Atlantic Ridge, between the European, American and African plate boundaries, forming their own microplate. The 1980 earthquake was the result of movement along a northwest to southeast trending strike-slip fault.

After aftershocks 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 in the right-lateral (dextral) direction. 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, São Jorge Island, and Graciosa), 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 such as electricity and water, were reported cut in several areas.

Initially, the number of fatalities was set at 52. Additionally, the injuries were set at 300, but this was also revised to more than 400. Minor damage was recorded at Pico and Faial islands.

No fatalities were recorded at the Lajes Field air base, nor any major damage.

Relief efforts and response

United States Navy and Air Force personnel stationed at Lajes functioned as disaster relief workers, Portuguese Air Force members brought supplies to earthquake victims, while a Portuguese Navy 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 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.

References

; Notes ; Sources

References

1. (January 1, 1980). "Significant Earthquake: AZORES: TERCEIRA, ANGRA DO HEROISMO". [[National Geophysical Data Center]].
2. Western Newspapers (2 January 1980)
3. Borges et al. (2007), p.37–54
4. Udías, Agustín. (1990). "Regional stresses along the Eurasia-Africa plate boundary derived from focal mechanisms of large earthquakes". Pure and Applied Geophysics.
5. Hirn, A.. (July 1980). "Aftershock sequence of the January 1, 1980, earthquake and present-day tectonics in the Azores". [[Geophysical Research Letters]].
6. (February 18, 2009). "Today in Earthquake History: January 1". United States Geological Survey.
7. (January 2, 1980). "Quake Hits Azores Islands; at Least 52 Die, 300 Hurt". Los Angeles Times.
8. Ferreira, Marta Leite. "Sismo dos Açores em 1980. A história do terramoto mais destrutivo dos últimos 200 anos em Portugal".
9. Mendes, Ana Isabel. (2014-03-08). "Memórias do sismo de 1980 nos Açores reunidas num “site”".
10. (January 2, 1980). "Earthquake Kills 52 in the Azores". The New York Times.
11. (October 3, 1982). "Azores' Exiles Forsake U.S. And Go Home". The New York Times.
12. "Lajes Field History – Humanitarian Efforts, 1980s and 1990s". Lajes Air Field.
13. Malheiro, A.. (August 2006). "Geological hazards in the Azores archipelago: Volcanic terrain instability and human vulnerability". [[Journal of Volcanology and Geothermal Research]].