1981 Irian Jaya earthquake
Encyclopedia
On January 19, 1981, eastern Indonesia was struck by an earthquake known as the 1981 Irian Jaya earthquake. Registering a magnitude of 6.8 on the Richter scale, it killed more than 300 people, damaging structures and buildings across the Irian Jaya province.
Indonesia is highly active in terms of seismicity and volcanic eruptions, with a subduction zone and many faults. It is neighbored by several tectonic plates. Such earthquakes pose a significant threat to life in the area through earthquakes and also tsunamis.
, composed by a subduction zone (in the Sunda Trench) and islands. Unlike most subduction zones, the Sunda Trench is parallel to the chain of islands to which it corresponds, creating strike-slip faulting. Indonesia itself is surrounded by multiple tectonic plates
- namely the Pacific
, the Southeast Asia lithospheric, and the Indo-Australian Plate
s - causing it to be a so-called hotspot for both seismic and volcanic activity.
The epicenter was in Papua Province, in the Irian Jaya Province. The orientation and type of faulting is uncertain, due to a poorly constrained focal mechanism
but is thought to have been a reverse fault.
.
The earthquake caused huge landslides, which cascaded into the villages below the mountains, destroying more than 150 homes. The debris from these flows blocked transportation by road, "cutting off more than 2,000 area residents". Relief efforts took several days.
, which killed more than 250,000 people. Earthquakes along the subduction zone at Sunda and on the Great Sumatran fault
pose a serious threat to life, especially in the form of tsunamis. A 2005 study found that stress on at least these two zones was at a heightened level, and both have been active. The Sunda Trench zone has since produced the July 2006 Java earthquake
, while the Great Sumatran fault has not produced an earthquake since the 2004 event.
Indonesia is highly active in terms of seismicity and volcanic eruptions, with a subduction zone and many faults. It is neighbored by several tectonic plates. Such earthquakes pose a significant threat to life in the area through earthquakes and also tsunamis.
Geology
Indonesia, one of the most seismically active places in the world, hosts hundreds of islands, many with volcanoes. It is an island arcIsland arc
An island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates....
, composed by a subduction zone (in the Sunda Trench) and islands. Unlike most subduction zones, the Sunda Trench is parallel to the chain of islands to which it corresponds, creating strike-slip faulting. Indonesia itself is surrounded by multiple tectonic plates
Tectonic Plates
Tectonic Plates is a 1992 independent Canadian film directed by Peter Mettler. Mettler also wrote the screenplay based on the play by Robert Lepage. The film stars Marie Gignac, Céline Bonnier and Robert Lepage.-Plot summary:...
- namely the Pacific
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million square kilometres, it is the largest tectonic plate....
, the Southeast Asia lithospheric, and the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
s - causing it to be a so-called hotspot for both seismic and volcanic activity.
The epicenter was in Papua Province, in the Irian Jaya Province. The orientation and type of faulting is uncertain, due to a poorly constrained focal mechanism
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...
but is thought to have been a reverse fault.
Damage and casualties
Spawning enormous landslides, the earthquake left at least 305 people dead and more than 1,000 missing. Entire villages were covered by debris. It was described as "strong" by The New York TimesThe New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...
.
The earthquake caused huge landslides, which cascaded into the villages below the mountains, destroying more than 150 homes. The debris from these flows blocked transportation by road, "cutting off more than 2,000 area residents". Relief efforts took several days.
Future threats
Indonesia is known for deadly earthquakes, primarily the 2004 Indian Ocean earthquake2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...
, which killed more than 250,000 people. Earthquakes along the subduction zone at Sunda and on the Great Sumatran fault
Great Sumatran fault
The Indonesian island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone and the associated Sunda Arc off the west coast of the island, Sumatra also has a large strike-slip fault, the so-called Great Sumatran Fault, running the entire length of the island...
pose a serious threat to life, especially in the form of tsunamis. A 2005 study found that stress on at least these two zones was at a heightened level, and both have been active. The Sunda Trench zone has since produced the July 2006 Java earthquake
July 2006 Java earthquake
The July 2006 Java earthquake was a magnitude 7.7 earthquake off the southwestern coast of Java, Indonesia. It occurred on July 17, 2006, at 08:24 UTC ....
, while the Great Sumatran fault has not produced an earthquake since the 2004 event.