Molucca Sea Plate

Located in the western Pacific Ocean near Indonesia, the Molucca Sea Plate has been classified by scientists as a fully subducted microplate that is part of the Molucca Sea Collision Complex. The Molucca Sea Plate represents the only known example of divergent double subduction (DDS), which describes the subduction on both sides of a single oceanic plate.[1]

MoluccaSeaCollisionZone
Molucca Sea Collision Zone modified by Zhang et al.[1] using GeoMapApp

Tectonic setting

The Molucca Sea Plate is one of many tectonic features that compose the Molucca Sea Collision Complex, which refers to the tectonic relationship of the Sangihe Plate, Halmahera Plate, and the Molucca Sea Plate, in addition to the volcanic Halmahera and Sangihe Arcs. The southeast moving Sangihe Plate is situated along the western boundary of the Molucca Sea Plate. The northwest moving Halmahera Plate is situated along the eastern boundary of the Molucca Sea Plate. In the western Pacific Ocean, the Molucca Sea is bordered by the Indonesian Islands of Celebes (Sulawesi) to the west, Halmahera to the east, and the Sula Islands to the south. The Molucca Sea borders the Banda Sea to the south and the Celebes Sea to the west. To the north is the Philippine Sea and to the east is the Halmahera Sea. Situated south of Mindanao, the Molucca Sea is a narrow basin underlined by a north‐south ophiolitic ridge, which uplifts the central region of the basin.[2]

Plate mechanics

CrossSection
Cross Section of Molucca Sea Collision Zone modified by Zhang et al.[1]

While the scientific community has not come to a consensus as to when the Molucca Sea Plate became fully subducted, the dominant theory is that the Molucca Sea Plate has been completely subducted beneath the overriding Halmahera and Sangihe Plates.[1] When actively subducting, the crustal collision of the Molucca Sea Plate was formed by surface intersection of “oppositely dipping Benioff zones” (also known as divergent double subduction) which results in the Sangihe and Halmahera volcanic arcs.[2] The force exerted by the thick overlying collision complex of the Halmahera and Sangihe Plates effectively depressed the crust of the Molucca Sea Plate.[3] The plate itself features an asymmetrical morphology, configured in an inverted U-shape. The arc-arc collision zone of the Molucca Sea Plate is characterized as a thick, low velocity layer, which is highly variable in density.[1][4] The variable in density of the Molucca Sea Plate led to different subduction velocities on the two sides.[1] Divergent Double Subduction may facilitate various tectonic processes, including closure of ocean basins, accretion and amalgamation of volcanic arcs, and growth of continents.[1]

Earthquakes

Divergent Double Subduction Zone
(Asymmetric) Divergent Double Subduction Zone modified by Zhao et al.[1]

Historically, the Molucca Sea Plate has experienced hundreds of earthquakes ranging in magnitude.[2] The most recent large earthquake occurred on January 2017 when a 7.3 magnitude earthquake deep beneath the Celebes Sea, which the USGS attributed to the “deep reverse faulting within the inclined seismic zone defining the deep limit of the Molucca Sea microplate beneath the Celebes Sea Basin.[5]

Geology

The geologic characteristics displayed on the surrounding islands provide insight regarding the complex plate movement of the divergent double subducting plate. Detached ophiolitic series and thick melanges are overlain by forearc deposits; subduction-driven east-west shortening of the Snellius Plateau caused the thrust melanges to reactivate and deform the forearc series.[6] Exposed ophiolitic rocks can be found on the islands of the submarine Talaud-Mayu Ridge, which bisects the arc-arc collision zone of the Molucca Sea Plate; these ophiolites provide insight regarding the relationship between earthquakes and uplift surrounding the plate.[7]

See also

References

  1. ^ a b c d e f g h Zhang, Qingwen; Guo, Feng; Zhao, Liang; Wu, Yangming (May 2017). "Geodynamics of divergent double subduction: 3-D numerical modeling of a Cenozoic example in the Molucca Sea region, Indonesia". Journal of Geophysical Research: Solid Earth. 122 (5): 3977–3998. doi:10.1002/2017jb013991. ISSN 2169-9313.
  2. ^ a b c Silver, Eli A.; Moore, J. Casey (1978-04-10). "The Molucca Sea Collision Zone, Indonesia". Journal of Geophysical Research: Solid Earth. 83 (B4): 1681–1691. doi:10.1029/jb083ib04p01681. ISSN 0148-0227.
  3. ^ McCaffre, Silver, Raitt, Robert, Eli, Russell (1980). "Crustal Structure of the Molucca Sea Collision Zone,Indonesia" (PDF). Geophysical Monograph. 23.CS1 maint: multiple names: authors list (link)
  4. ^ McCaffrey, Robert; Silver, Eli A.; Raitt, Russell W. (1980). The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands. Washington, D. C.: American Geophysical Union. pp. 161–177. doi:10.1029/gm023p0161. ISBN 978-0875900230.
  5. ^ "Philippines, Iran, Alaska (and the Far North): Earthquakes 5-11 January 2017". Decoded Science. 2017-01-11. Retrieved 2018-06-03.
  6. ^ Bader, Anne Gaëlle; Pubellier, Manuel (2008-07-18). "Forearc deformation and tectonic significance of the ultramafic Molucca central ridge, Talaud islands (Indonesia)". Island Arc. 9 (4): 653–663. doi:10.1111/j.1440-1738.2000.00309.x. ISSN 1038-4871.
  7. ^ McCaffrey, Robert (April 1991). "Earthquakes and ophiolite emplacement in the Molucca Sea Collision Zone, Indonesia". Tectonics. 10 (2): 433–453. doi:10.1029/90tc02553. ISSN 0278-7407.
2010 Mindanao earthquakes

The 2010 Mindanao earthquakes occurred in the southern Philippines in the Moro Gulf. This was a complex sequence of events including three man events (a triplet earthquake) of Mw magnitude 7.3 or greater on the 23rd of July, and two significant aftershocks of magnitude 6.6 on the 24th and 29th. All of these were deep focus earthquakes, at depths from 565 km (351 mi) to 634 km (394 mi). This results in minimal shaking at the surface; consequently there were no reports of casualties or damage.

2019 North Maluku earthquake

The 2019 North Maluku earthquake, a shallow 7.2 magnitude earthquake, struck the island of Halmahera, North Maluku, Indonesia on 14 July 2019 at 18:10 local time with its epicentre located at South Halmahera. It struck at a shallow depth of 10 km (6.2 mi) near Labuha, a small port town located in Bacan Island. The earthquake produced a non-destructive 20 cm tsunami, which stuck Labuha just minutes after the shaking started. 14 people were killed by the earthquake while 129 people were injured, and more than 50,000 people were displaced. The earthquake inflicted a total damage of Rp 238 billion (USD 16 million).

Cotabato Trench

The Cotabato Trench is an oceanic trench in the Pacific Ocean, off the southwestern coast of Mindanao in the Philippines. Along this trench the oceanic crust of the Sunda Plate beneath the Celebes Sea is being subducted beneath the Philippines Mobile Belt. It forms part of a linked

set of trenches along the western side of the Philippines formed over east-dipping subduction zones, including the Manila Trench and the Negros Trench. At its northern end the rate of convergence across this boundary is about 100 mm per year. It is a relatively young structure, forming during the late Miocene to Pliocene. This age is consistent with the estimated age of the sedimentary rocks in the accretionary wedge associated with the trench and the age of adakitic arc rocks on Mindanao thought to date the onset of subduction.

Divergent double subduction

Divergent double subduction (abbreviated to DDS, also called as outward dipping double-sided subduction) is a special type of subduction system where two parallel subduction zones with different directions are developed on the same oceanic plate. In conventional plate tectonics theory, an oceanic plate subducts under another plate and new oceanic crust is generated somewhere else, commonly along the other side of the same plates However, in divergent double subduction, the oceanic plate subducts on two sides. This results in the closure of ocean and arc-arc collision. This concept was first proposed and applied to the Lachlan fold belt in southern Australia. Since then, geologists have applied this model to other regions such as the Solonker Suture Zone of the Central Asian Orogenic belt, the Jiangnan Orogen, the Lhasa–Qiangtang collision zone and the Baker terrane boundary. Active examples of this system are 1) the Molucca Sea Collision Zone in Indonesia, in which the Molucca Sea plate subducts below the Eurasian plate and the Philippine Sea plate on two sides, and 2) the Adria microplate in the Central Mediterranean, subducting both on its western side (beneath the Apennines and Calabria) and on its eastern side (beneath the Dinarides). Note that the term "divergent" is used to describe one oceanic plate subducting in different directions on two opposite sides. It should not be confused with use of the same term in 'divergent plate boundary' which refers to a spreading center that separates two plates moving away from each other.

Geography of Indonesia

Indonesia is an archipelagic country located in Southeast Asia, lying between the Indian Ocean and the Pacific Ocean. It is located in a strategic location astride or along major sea lanes connecting East Asia, South Asia and Oceania. It is the world's largest island country. Indonesia's various regional cultures have been shaped—although not specifically determined—by centuries of complex interactions with its physical environment.

Geology of the Pacific Ocean

The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.The tectonic plates continue to move today. The slowest spreading ridge is the Gakkel Ridge on the Arctic Ocean floor, which spreads at less than 2.5 cm/year (1 in/year), while the fastest, the East Pacific Rise near Easter Island, has a spreading rate of over 15 cm/year (6 in/year).

Halmahera Arc

Halmahera Arc is the volcanic arc of the Halmahera region of eastern Indonesia. It is considered to belong to the Halmahera Plate tectonics, within the Molucca Sea Collision Zone.

Halmahera Plate

Halmahera Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

List of tectonic plates

This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.

Manila Trench

The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about 5,400 metres (17,700 ft), in contrast with the average depth of the South China Sea of about 1,500 metres (4,900 ft). It is created by subduction, in which the Sunda Plate (part of Eurasian Plate) is subducting under the Philippine Mobile Belt, producing this almost N-S trending trench. The convergent boundary is terminated to the north by the Taiwan collision zone, and to the south by the Mindoro terrane (Sulu-Palawan block colliding with SW Luzon). It is an area pervaded by negative gravity anomalies.The Manila Trench is associated with frequent earthquakes, and the subduction zone is responsible for the belt of volcanoes on the west side of the Philippine island of Luzon, which includes Mount Pinatubo.

Convergence between the Philippine Mobile Belt and the Sunda Plate have been estimated using GPS measurements, and this value ranges from ~ 50+ mm/yr in Taiwan, to 100 mm/yr near N. Luzon, and ~ 50 mm/yr near Zambales and ~20+mm/yr near Mindoro island. Plate locking between the Sunda Plate and Luzon is about 1% coupled, almost unlocked as determined by elastic block models, suggesting that the trench absorbs the Philippine Mobile Belt-Eurasian Plate convergence.

Marikina Valley Fault System

The Marikina Valley Fault System, also known as the Valley Fault System (VFS), is a dominantly dextral strike-slip fault system in Luzon, Philippines. It extends from Doña Remedios Trinidad, Bulacan in the north and runs through the provinces of Rizal, and the Metro Manila cities of Quezon, Marikina, Pasig, Makati, Taguig and Muntinlupa, and the provinces of Cavite and Laguna that ends in Canlubang.

Molucca Sea

The Moluccan Sea (Indonesian: Laut Maluku) is located in the western Pacific Ocean, around the vicinity of Indonesia, specifically bordered by the Indonesian Islands of Celebes (Sulawesi) to the west, Halmahera to the east, and the Sula Islands to the south. The Molucca Sea has a total surface area of 77,000 square miles (200,000 square km). The Molucca Sea is rich in coral and has many diving sites due to the deepness of its waters. The deepness of the water explains the reasoning behind dividing the sea into three zones, which functions to transport water from the Pacific Ocean to the shallower seas surrounding it. The deepest hollow in the Molucca Sea is the 15,780-foot (4,810-meter) Batjan (Indonesian: Bacan) basin. This region is known for its periodic experiences of earthquakes, which stems from the sea itself being a micro plate, in which the Molucca Sea is being subducted in two opposite directions: one in the direction of the Eurasian Plate to the west and the other in the direction of the Philippines Sea Plate to the east.

Molucca Sea Collision Zone

The Molucca Sea Collision Zone is postulated by paleogeologists to explain the tectonics of the area based on the Molucca Sea in Indonesia, and adjacent involved areas.

Outline of plate tectonics

This is a list of articles related to plate tectonics and tectonic plates.

Philippine Mobile Belt

The Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine Fault System. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is bounded by the Philippine Sea Plate to the east, the Molucca Sea Collision Zone to the south, Sunda Plate to the southwest, and the South China Sea Basin to the west and north-west. To the north it ends in eastern Taiwan, the zone of active collision between the North Luzon Trough portion of the Luzon Volcanic Arc and South China. The Philippine Mobile Belt has also been called the Philippine Microplate and the Taiwan-Luzon-Mindoro Belt.

Sangihe Plate

Sangihe Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.

Sorong Fault

Sorong fault also (Sorong Fault Zone, SFZ) is an active, broad zone of inferred left lateral shear at the triple junction of the Australian plate, Eurasian plate, and Pacific plates, where many plate fragments exist, such as the Philippine Sea Plate, Bird's Head Plate, Halmahera Plate and the Molucca Sea Plate. It has been implicated in numerous large earthquakes. It is one of the two major faults created by the Australian and Pacific plate convergence, the other being the Ramu-Markham Fault zone.

Sunda Plate

The Sunda Plate is a minor tectonic plate straddling the equator in the eastern hemisphere on which the majority of Southeast Asia is located.The Sunda Plate was formerly considered a part of the Eurasian Plate, but GPS measurements have confirmed its independent movement at 10 mm/yr eastward relative to Eurasia.

Talaud Islands

Talaud Islands (Indonesian: Kepulauan Talaud) is a group of islands located north of Sulawesi island in Indonesia, north-east of the Sangihe Islands. The Talaud Islands are also the northernmost region of Eastern Indonesia, bordering south of the Philippines' Davao Region.

The group, with a total area of 495 square miles (1,281 square km), includes Karakelong (the largest), Salebabu, Kaburuang, and numerous islets. The coast of Karakelong Island is steep except on the southern shore, which is fringed by a wide reef. The seven tiny Nanusa Islands lie north-east of Karakelong. They are forested and with hills rising to 2,231 feet (680 metres).

Major
Minor
Other
Historical
Tectonic plates of Southeast Asia–New Guinea (Australian Plate-Pacific Plate Convergence Zone)
Large
Small
Faults
Trenches
and troughs
Subsea plateaus
and basins

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