![Japan Trench](https://upload.wikimedia.org/wikipedia/commons/7/76/Japan_Trench.png)
The Japan Trench is an
oceanic trench
Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic tren ...
part of the
Pacific Ring of Fire
The Ring of Fire (also known as the Pacific Ring of Fire, the Rim of Fire, the Girdle of Fire or the Circum-Pacific belt) is a region around much of the rim of the Pacific Ocean where many Types of volcanic eruptions, volcanic eruptions and ...
off northeast Japan. It extends from the
Kuril Islands
The Kuril Islands or Kurile Islands (; rus, Кури́льские острова́, r=Kuril'skiye ostrova, p=kʊˈrʲilʲskʲɪjə ɐstrɐˈva; Japanese: or ) are a volcanic archipelago currently administered as part of Sakhalin Oblast in the ...
to the northern end of the
Izu Islands
The are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshū, Japan. Administratively, they form two towns and six villages; all part of Tokyo Prefecture. The largest is Izu Ōshima, usually called simply Ō ...
, and is at its deepest. It links the
Kuril–Kamchatka Trench
The Kuril–Kamchatka Trench or Kuril Trench (russian: Курило-Камчатский жёлоб, ''Kurilo-Kamchatskii Zhyolob'') is an oceanic trench in the northwest Pacific Ocean. It lies off the southeast coast of Kamchatka and parallels ...
to the north and the
Izu–Ogasawara Trench
The , also known as Izu–Bonin Trench, is an oceanic trench in the western Pacific Ocean, consisting of the Izu Trench (at the north) and the Bonin Trench (at the south, west of the Ogasawara Plateau).
It stretches from Japan to the northernmost ...
to its south with a length of . This trench is created as the oceanic
Pacific plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate.
The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...
subducts beneath the continental
Okhotsk Plate
The Okhotsk Plate is a minor tectonic plate covering the Kamchatka Peninsula, Magadan Oblast, and Sakhalin Island of Russia; Hokkaido, Kantō and Tōhoku regions of Japan; the Sea of Okhotsk, as well as the disputed Kuril Islands. It was ...
(a microplate formerly a part of the
North American Plate
The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...
). The subduction process causes bending of the down going plate, creating a deep trench. Continuing movement on the subduction zone associated with the Japan Trench is one of the main causes of
tsunamis
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 expl ...
and
earthquakes
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, from ...
in northern Japan, including the
megathrust
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqu ...
Tōhoku earthquake and resulting tsunami that occurred on 11 March 2011. The rate of subduction associated with the Japan Trench has been recorded at about /yr.
Tectonic history
During the late
Neogene
The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
period (23.03-2.58 million years ago), the Japan Trench underwent a period of plate convergence between the Pacific and Okhotsk plates. Based on the sediment sequence during this time, there appears to have been little net accretion of sediment onto the overlying plate as well as evidence of mild erosion at the base of the convergent margin.
During the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
(145.5-66 million years ago) to early
Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
(66-23.03 ma), evidence of
andesitic
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...
along with the development of a large
syncline
In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimpose ...
and a thickened sediment sequence indicate the possible development of a
forearc basin
Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the vol ...
. Activity during the Cretaceous included subduction events as well as extensive accretion of sediment to the
Northeastern Japan Arc that continues today. Volcanism decreased during the early Paleogene (66 ma), exposing the thickened Cretaceous-Paleogene thick sediment sequence. Once this sediment sequence subsided, volcanism once again resumed.
Seismicity
Seismic activity along the Japan Trench occurs along the associated subduction zone at disruptive convergent plate boundaries between the Okhotsk and subducting Pacific plate. The continuing movement along these plate boundaries occur at a depth of about .
Seismic events
During the year of 1896, a magnitude (M) 6.8 earthquake was recorded within the Japan Trench. Later during the same year, a destructive
magnitude 8.5 earthquake occurred resulting in two tsunamis wreaking havoc.
A series of M7 earthquakes occurred at the Fukushima-oki region in 1938, registering five in total. The magnitudes were 7.4, 7.7, 7.8, 7.7 and 7.1.
During December 1994, transient crustal movements were recorded by a Global Positioning System (GPS) network after an inter-plate earthquake arose within the Japan Trench. This very subtle, but distinct disruption observed indicates a "silent" slow fault slip was triggered by this. A recorded magnitude 7.7 earthquake was recorded in Sanriku-oki that may have been triggered by the slow slip observed earlier.
Many other earthquakes have been recorded from interplate and transient postseismic slip data along the Japan Trench. Dates include August 2005, May 2008, July 2008, and March 2010 ranging in magnitudes 7.2, 7.0, 6.9, and 6.7 respectively. A characteristic earthquake (~M7) periodically occurred at a recurring interval rate of about 37 years. ~M7 earthquakes can be seen in the table to the right, occurring in the years 1938, 1989, 1992, 2005, 2008, 2008 and 2011.
Ocean bottom
seismometer
A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...
s placed in the base of the Japan Trench measures the ground for any motion created by recording the seismic waves emitted. In 2012, the National Research Institute for Earth Science and Disaster Resilience (NIED) stationed in Tokyo started the construction of seismic and tsunami observation networks along the trench. They planned to layout 154 stations about apart, each equipped with an
accelerometer
An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...
to observe seismic changes and a water pressure gauge for tsunami observation.
2011 Tōhoku earthquake
On March 11, 2011, a magnitude 9.0 earthquake occurred on the subduction interface boundary of the Pacific Plate sinking underneath Japan along the Japan Trench. A rupture within the central region of the trench spanning an area of about long and wide resulted here. It is considered as the most powerful earthquake ever recorded in Japan as well as one of the four most powerful earthquakes ever recorded since the start of modern record-keeping in 1900. This
megathrust earthquake
Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqua ...
caused giant tsunami waves to form which eventually caused destruction to the coastline of northern Japan. The damage left about 16,000 people killed along with a catastrophic level 7
nuclear meltdown
A nuclear meltdown (core meltdown, core melt accident, meltdown or partial core melt) is a severe nuclear reactor accident that results in core damage from overheating. The term ''nuclear meltdown'' is not officially defined by the Internation ...
of three nuclear reactors located at the
Fukushima Daiichi Nuclear Power Plant
The is a disabled nuclear power plant located on a site in the towns of Ōkuma and Futaba in Fukushima Prefecture, Japan. The plant suffered major damage from the magnitude 9.0 earthquake and tsunami that hit Japan on March 11, 2011. The ...
complex. The World's Bank recorded the total cost of damage to be about US$235 billion, making it the
costliest natural disaster in history.
Surface roughness
Large
magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...
and frequent earthquake activity occurring at the northern Japan Trench may be explained by variations in surface roughness of the subducting Pacific plate. Regions of smooth ocean floor subduction are correlated with typically large under-thrust earthquakes within the deeper part of the plate interface zone. No earthquakes have been observed or reported from the shallow aseismic zone of the north Japan Trench. Regions of rough ocean bottom subduction are correlated with large
normal fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tecton ...
ing earthquakes within the outer-rise region, along with larger tsunami earthquakes occurring at the shallow region of the plate interface (megathrust events) .
Ocean drilling
![Japan_Trench_Drilling_Site](https://upload.wikimedia.org/wikipedia/commons/9/96/Japan_Trench_Drilling_Site.jpg)
In 1980,
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s samples were taken via sediment cores located on both the landward and distal sides of the Japan Trench during six sections of the Deep Sea Drilling Project's transect. They were analyzed using
gas chromatography
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...
and computerized-gas
chromatography-mass spectrometric data. Samples were identified to contain many components such as aliphatic and aromatic hydrocarbons, ketones, alcohols, acids and other poly functional components. These components are considered as indicators for terrestrial, marine (non-bacterial), and bacterial inputs within the sediment of the Japan Trench.
Expedition 343 of the Japan Trench Fast Driling Project was conducted under the supervision and authority of the Japan Agency For Marine-Earth Science and Technology (
JAMSTEC). The drilling occurred during two periods; April 1 to May 24, 2012 and from July 5th-18th, 2012. Their main goal was to better understand the very large fault slip of that occurred during the Tohoku earthquake and its potential as one of the main triggers of tsunami wave formation occurring along the northeast coast of Japan.
In 2013, the Integrated Ocean Drilling Program (IODP) Expedition 343 collected sediment samples from drilling at the plate boundary fault zone along the Japan Trench. The sediment cores collected exhibited low friction at coseismic slip velocities as well as at low slip velocities. These studies and samples have supported the idea that these frictional properties of the fault zone possibly triggered the shallow and large slip during the Tohoku earthquake.
Sediments
Turbidite paleoseismology
Sediment samples within the Japan Trench consist mainly of highly localized clay-rich material. The subducting Pacific Plate creates basins along the ocean floor of the Japan Trench, accommodating the deposition of fine-grained
turbidite
A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean.
Sequencing
Turbidites were ...
s and interseismic sediment deposits through
turbidity current
A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. T ...
s. These turbidites preserve the sediment deposits as a geologic record of past large earthquakes by indicating the change in sediment deposition through
sediment gravity flow
upright=1.25, This turbidite from the Devonian Becke-Oese Sandstone">Devonian.html" ;"title="turbidite from the Devonian">turbidite from the Devonian Becke-Oese Sandstone of Germany is an example of a deposit from a sediment gravity flow. Note th ...
. The small deep-sea basins with high sedimentation rates found along the Japan Trench pose favorable environmental conditions for the studying of turbidite
paleoseismology
Paleoseismology looks at geologic sediments and rocks, for signs of ancient earthquakes. It is used to supplement seismic monitoring, for the calculation of seismic hazard. Paleoseismology is usually restricted to geologic regimes that have ...
.
Microbial activity
During an exploration to the Japan Trench on January 1, 1999, a sample of deep-sea sediment was taken from a depth of from the use of a pressure-retaining sediment sampler. Samples from the expedition showed that the microbial diversity displayed a wide distribution of types in the
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
domain.
16S ribosomal RNA
16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure.
The genes coding for it are referred to as 16S rRNA ...
genes were amplified through the use of
polymerase chain reaction (PCR)
The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
to determine the
nucleotide
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules wi ...
s and identify the bacteria
phylogenetically
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
. Further analysis of
fatty acid
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...
s extracted from the same cultures further supported the phylogenetic results observed. The discovery of different bacterial domains in these sediments can be used as indicators for microbial diversity found within the Japan Trench.
Exploration
*In 1987, results from the French-Japanese Kaiko exploration program into the Japan Trench along with complementary data were used to create and propose a model of the subduction of seamount chains between the Japan and Kuril trenches as well as along the southern part of the Japan Trench.
*On 11 August 1989, the
Shinkai 6500
The ''Shinkai 6500'' (しんかい) is a crewed research submersible that can dive up to a depth of . It was completed in 1990 and had the greatest depth range of any crewed research vehicle in the world until June 19, 2012, when its record wa ...
three-person submersible descended to while exploring the Japan Trench.
*In October 2008, a UK-Japan team discovered a shoal of ''
Pseudoliparis amblystomopsis
''Pseudoliparis amblystomopsis'', or the hadal snailfish, is a species of snailfish from the hadal zone of the Northwest Pacific Ocean, including the Kuril–Kamchatka and Japan Trenches.
In October 2008, a team from British and Japanese instit ...
'' snailfish at a depth of approximately in the trench. These were, at the time, the deepest living fish ever filmed. The record was surpassed by an unidentified type of snailfish filmed at a depth of in December 2014 in the
Mariana Trench
The Mariana Trench is an oceanic trench located in the western Pacific Ocean, about east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about in length and in width. The maximum know ...
, and extended in May 2017 when another unidentified type of snailfish was filmed at a depth of in the Mariana Trench.
See also
*
Izu–Bonin–Mariana Arc
The Izu–Bonin–Mariana (IBM) arc system is a plate tectonics, tectonic plate convergent boundary in Micronesia. The IBM arc system extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, the Bonin Island ...
References
;Notes
External links
*
{{East Asia plates
Oceanic trenches of the Pacific Ocean
Landforms of Japan
Subduction zones