The 1996 Biak earthquake, or the Irian Jaya earthquake, occurred on 17 February at near Biak Island, Indonesia. The

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

, which occurred on the New Guinea Trench, had a

moment magnitude 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 ...

of 8.2 and a maximum

Mercalli intensity The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

of IX (''Violent''). The run-up height of the generated

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

reached . The disaster left at least 108 people dead, 423 injured, and 58 missing. It damaged or destroyed 5,043 houses which subsequently made another 10,000 homeless. At Korim, 187 houses were destroyed. Various countries and organizations provided aid and relief in the aftermath of the earthquake.

Tectonic setting

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...

lies within a very complex tectonic regime surrounded by microplates which accommodate the collision and oblique convergence between the

Australian Plate The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke ...

and the Pacific Plate. In the north, the

Caroline Plate The Caroline Plate is a minor tectonic plate that straddles the Equator in the eastern hemisphere located north of New Guinea. It forms a subduction zone along the border with the Bird's Head Plate and the Woodlark Plate to the south. A transfo ...

and

North Bismarck Plate The North Bismarck Plate is a small tectonic plate located in the Bismarck Sea off the northeast coast of New Guinea. Tectonics To the north it collides with the Pacific Plate and the Caroline Plate, part of the western part subducts under the W ...

subduct underneath the

Bird's Head Plate The Bird's Head Plate is a minor tectonic plate incorporating the Bird's Head Peninsula, at the western end of the island of New Guinea. Hillis and Müller consider it to be moving in unison with the Pacific Plate. Bird considers it to be unconne ...

and the

Woodlark Plate The Woodlark Plate is a small tectonic plate located in the eastern half of the island of New Guinea. It subducts beneath the Caroline plate along its northern border while the Maoke Plate converges on the west, the Australian plate converges on ...

along the

New Guinea Trench New is an adjective referring to something recently made, discovered, or created. New or NEW may refer to: Music * New, singer of K-pop group The Boyz Albums and EPs * ''New'' (album), by Paul McCartney, 2013 * ''New'' (EP), by Regurgitator, ...

. The earthquake occurred at the central portion of the trench. The western portion of New Guinea has parallel subduction zones to the north and south of it along a continuation of the

Philippine Trench The Philippine Trench (also Philippine Deep, Mindanao Trench, and Mindanao Deep) is a submarine trench to the east of the Philippines. The trench is located in the Philippine sea of the western North Pacific Ocean and continues NNW-SSE. It has a ...

and a convergent boundary between the Bird's Head Plate and the

Banda Sea Plate The Banda Sea Plate is a minor tectonic plate underlying the Banda Sea in southeast Asia. This plate also carries a portion of Sulawesi Island, the entire Seram Island, and the Banda Islands. Clockwise from the east it is bounded by the Bird's Hea ...

. In western central New Guinea, the

Maoke Plate The Maoke Plate is a small tectonic plate located in western New Guinea underlying the Sudirman Range from which the highest mountain on the island- Puncak Jaya rises. To its east is a convergent boundary with the Woodlark Plate. To the south lies ...

has multiple boundaries with various plates. At the far eastern portion of the island, the South Bismarck Plate interacts with the Woodlark Plate, as well as the

Solomon Sea Plate The Solomon Sea Plate is a minor tectonic plate to the northwest of the Solomon Islands archipelago in the south Pacific Ocean. Itt roughly corresponds with the Solomon Sea east of Papua New Guinea. Tectonics The tectonic regime in this part of t ...

subducting underneath the Woodlark Plate. The largest on-land plate boundary in the region, however, is between the Woodlark Plate and the Australian Plate. Though generally considered largely aseismic before this earthquake, this region of the New Guinea Trench may have experienced a similar large earthquake in 1914.

Earthquake

Focal mechanisms indicate shallow-

angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the '' vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles a ...

reverse faulting which is consistent with a subduction zone rupture. It ruptured an area long and wide along the

oceanic

trench A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches result from ero ...

with an average

slip Slip or SLIP may refer to: Science and technology Biology * Slip (fish), also known as Black Sole * Slip (horticulture), a small cutting of a plant as a specimen or for grafting * Muscle slip, a branching of a muscle, in anatomy Computing and ...

of . From the

hypocenter In seismology, a hypocenter or hypocentre () is the point of origin of an earthquake or a subsurface nuclear explosion. A synonym is the focus of an earthquake. Earthquakes An earthquake's hypocenter is the position where the strain energy ...

, the rupture propagated to the west before propagating another east, ~15 seconds later. The largest slip was ~ near the hypocenter. Large aftershocks struck the area, with various focal mechanisms. The mainshock may have triggered nearby seismic structures to activate. Aftershocks were most common in the areas with the highest slip from the mainshock.

Tsunami

At Madori, on the west coast of Biak, a run-up of was measured, while at Korem in northern Biak, waves were up to . The tsunami also affected parts of nearby islands, including

Yapen Yapen (also Japan, Jobi) is an island of Papua, Indonesia. The Yapen Strait separates Yapen and the Biak Islands to the north. It is in Cenderawasih Bay off the north-western coast of the island of New Guinea. To the west is Mios Num Island ...

, Owi, and Pai, where waves of were measured. Roughly five minutes after the shaking, nearby residents heard an extraordinarily loud sound, such as one from an airplane, which they understood as a signal that a large wave was approaching. The local coastal population fled for higher ground as result. This action is credited with saving many lives from the tsunami. The tsunami produced was larger than expected for the size and location of the earthquake. A localized

submarine landslide Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress (gravity and other factors) exceeds the resisting str ...

was a plausible explanation for the strong waves in western Biak. This is further supported by the west coast of Biak being struck by the tsunami first, despite facing away from the main tsunami source. This does not align with a traditional shallow earthquake rupture tsunami, which further lends credence to the theory of a submarine landslide in the area near Madori. Multiple landslides were reported in the area near the maximum run-up height.

Aftermath

Domestic relief efforts

Immediately after the earthquake, the government of Indonesia provided rice to the affected. Some time after, the government, army, and

Red Cross The International Red Cross and Red Crescent Movement is a humanitarian movement with approximately 97 million volunteers, members and staff worldwide. It was founded to protect human life and health, to ensure respect for all human beings, and ...

evacuated affected individuals, distributed aid, and constructed a mass kitchen for 1,000 residents. Transportation was a challenge as bad weather and high waves stopped boats from being able to effectively deliver relief. A team involving members of multiple governmental ministries, and the agency for National Logistics Administration airlifted 36 tents, 5,300 blankets, of medicine, ambulances, water pumps, water containers, water, clothing, food, kerosene lamps, and plastic sheeting. The

Ministry of Social Affairs A Ministry of Social Affairs or Department of Social Affairs is the common name for a government department found in states where the government is divided into ministries or departments. While there is some variation in the responsibilities of ...

later delivered a further US$15,486 of food, 34 tons of rice, and "other immediate relief items". The Indonesian public donated US$74,588, as well as food items and building materials. The

First Lady of Indonesia Throughout Indonesian history, the title of First Lady ( id, Ibu Negara) or, in an instance, First Gentleman ( id, Bapak Negara) has been used to refer to the wife or husband of the president of Indonesia. While the Constitution of Indonesia does ...

contributed US$63,938 in cash, as well as 8,000 pieces of clothing.

International relief efforts

The

UNDP The United Nations Development Programme (UNDP)french: Programme des Nations unies pour le développement, PNUD is a United Nations agency tasked with helping countries eliminate poverty and achieve sustainable economic growth and human dev ...

donated US$25,000 for blankets, plastic sheeting, and food. Australia donated US$55,555 for emergency relief items and to cover the costs of relief operations carried out by helicopter. Japan donated US$84,000 toward a three-member team of experts to help assess damage and to assist in relief operations. An additional US$192,000 was provided to cover the costs of airlifting tents, water tanks, generators, carpentry kits, and medical equipment, and another US$200,000 to help locals buy relief items. As well, the government of

Yamagata Prefecture is a prefecture of Japan located in the Tōhoku region of Honshu. Yamagata Prefecture has a population of 1,079,950 (1 June 2019) and has a geographic area of 9,325 km² (3,600 sq mi). Yamagata Prefecture borders Akita Prefecture to the nor ...

chipped in US$9,346.

USAID The United States Agency for International Development (USAID) is an independent agency of the U.S. federal government that is primarily responsible for administering civilian foreign aid and development assistance. With a budget of over $27 bi ...

donated US$265,486 for housing (plastic sheeting, tents, blankets), US$10,000 to help with distributing relief as well as a two-member assessment team. Another US$10,000 was to distribute relief items. The Association of Medical Doctors of Asia contributed a team of three doctors with supplies and tools to help treat the injured.

References

External links

M 8.2 - Biak region, Indonesia
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United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

* {{Earthquakes in Indonesia Biak Earthquake

Earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

Megathrust earthquakes in Indonesia Biak earthquake 1996 Biak earthquake Biak earthquake Biak earthquake Biak earthquake Biak earthquake 1996 disasters in Indonesia