The Tōkai earthquakes () are major

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, from ...

s that have occurred regularly with a

return period A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, landslides, or river discharge flows to occur. It is a statistical measurement typ ...

of 100 to 150 years in the

Tōkai region The is a subregion of the Chūbu region and Kansai region in Japan that runs along the Pacific Ocean. The name comes from the Tōkaidō, one of the Edo Five Routes. Because Tōkai is a sub-region and is not officially classified, there is s ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. The Tōkai segment has been struck by earthquakes in 1498, 1605, 1707, 1854, and 1923. Given the historic regularity of these earthquakes,

Kiyoo Mogi was a prominent seismologist. He was regarded as Japan's foremost authority on earthquake prediction

in 1969 pointed out that another great shallow earthquake was possible in the "near future" (i.e., in the next few decades). Given the magnitude of the last two earthquakes, the next is expected to have at least a magnitude scale of 8.0 , with large areas shaken at the highest level in the Japanese intensity scale, 7. Emergency planners are anticipating and preparing for potential scenarios after such an earthquake, including the possibility of thousands of deaths and hundreds of thousands of injuries, millions of damaged buildings, and cities that include Nagoya and Shizuoka devastated. Concern has been expressed over the presence of the

Hamaoka Nuclear Power Plant The is a nuclear power plant in the city of Omaezaki in Shizuoka Prefecture, on Japan's east coast, 200 km south-west of Tokyo. It is managed by the Chubu Electric Power Company. There are five units contained at a single site with a net ...

, close to the expected epicentre of a Tōkai earthquake. The

Fukushima I Nuclear Power Plant may refer to: Japan * Fukushima Prefecture, Japanese prefecture **Fukushima, Fukushima, capital city of Fukushima Prefecture, Japan *** Fukushima University, national university in Japan *** Fukushima Station (Fukushima) in Fukushima, Fukushim ...

was severely damaged after a large earthquake followed by a tsunami in 2011, causing a nuclear event of level 7, the highest on the scale. Shortly after the 2011 Tōhoku earthquake, new reports were released which indicated the significant likelihood of another magnitude 9 earthquake occurring elsewhere in Japan, this time on the

Nankai Trough The is a submarine trough located south of the Nankaidō region of Japan's island of Honshu, extending approximately offshore. The underlying fault, the ''Nankai megathrust,'' is the source of the devastating Nankai megathrust earthquakes, wh ...

. The reports stated that if a 9.0 earthquake occurred on the Nankai Trough, the effects would be very serious. The quake itself would likely kill thousands, and a series of 34-meter (112-foot) tall tsunamis would impact areas from the

Kantō region The is a geographical area of Honshu, the largest island of Japan. In a common definition, the region includes the Greater Tokyo Area and encompasses seven prefectures: Gunma, Tochigi, Ibaraki, Saitama, Tokyo, Chiba and Kanagawa. Slight ...

Kyūshū is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surround ...

, adding thousands to the death toll, and destroying

Shizuoka Shizuoka can refer to: * Shizuoka Prefecture, a Japanese prefecture * Shizuoka (city), the capital city of Shizuoka Prefecture * Shizuoka Airport * Shizuoka Domain, the name from 1868 to 1871 for Sunpu Domain, a predecessor of Shizuoka Prefecture ...

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), '' ...

, and other areas with large populations.

Earthquake prediction

The Tokai Earthquake is expected to occur in the near future along the trench near

Suruga Bay Suruga Bay (駿河湾, ''Suruga-wan'') is a bay on the Pacific coast of Honshū in Shizuoka Prefecture, Japan. It is situated north of a straight line from Omaezaki Point to Irōzaki Point at the tip of the Izu Peninsula and surrounded by Honshū ...

with a magnitude of around 8. The Tokai region will be subjected to extremely strong shaking with seismic intensity of 6-lower or greater, and huge tsunamis are expected to hit the Pacific coast in the region. The Japanese government is taking the Tōkai earthquakes seriously and has charged the

Japan Meteorological Agency The , abbreviated JMA, is an agency of the Ministry of Land, Infrastructure, Transport and Tourism. It is charged with gathering and providing results for the public in Japan that are obtained from data based on daily scientific observation an ...

with predicting the next one. There is now a dense array of instruments placed to accumulate a continuous stream of data related to seismicity, strain, crustal expansion, tilt, tidal variations, ground water fluctuations and other variables. They are watching for an anomaly in this data which might precede the next major Tōkai earthquake. Following the prediction of an earthquake in the relatively near future, and in order to try to predict when it would occur, the

Coordinating Committee for Earthquake Prediction The Coordinating Committee for Earthquake Prediction (CCEP) (Japanese: 地震予知連絡会, ''Jishin Yochi Renraku-kai'') in Japan was founded in April 1969,

(CCEP) designated the Tōkai region as an Area of Specific Observation in 1970, and upgraded it to an Area of Intensified Observation in 1974. Following the passing of the Large-Scale Earthquake Countermeasure Act in 1978, the

Earthquake Assessment Committee 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 ...

(EAC) was set up to warn the Prime Minister, via the Japan Meteorological Agency, if the next quake is imminent.Information on the Tokai Earthquake
- JMA

As serious damage from strong shaking and huge tsunamis is expected, the Japanese government has designated this region as Areas under Intensified Measures against Earthquake Disaster. Information on future quakes is published irregularly. Since November 2017, this information limited to Tokai earthquakes has not been announced, and "Information on the Nankai megathrust earthquake ( 南海トラフ地震に関連する情報) " targeting the Nankai megathrust earthquakes has been in operation.南海トラフ地震について
気象庁 Future Tokai earthquakes are expected to occur with the sequence of # strain accumulation, # pre-slip and # earthquake occurrence. JMA monitors unusual deformation that may accompany

pre-slip In seismology, pre-slip is a phenomenon in which part of a hard bonded region underground detaches and begins to slip by slow. It often occurs before a major earthquake occurs at the plate boundary.

using strainmeters to support the prediction of its occurrence. As pre-slip may be too slight to be detected by the observation systems currently in place, it is not possible to say that the Tokai Earthquake will be predicted without fail.

Prediction information

To support predictions, JMA has developed a seismic and crustal deformation observation network covering the region in conjunction with related organizations, and observes related data around-the-clock basis. After monthly assessments, or when anomalous data are detected, JMA issues Information on the Tokai Earthquake bulletins to allow emergency measures for earthquake disaster prevention. These are categorized into three types: Investigation Report on Tokai Earthquake Prediction, Tokai Earthquake Watch, and Explanatory Information on Tokai Earthquake Warning. Each report indicates the level of danger using a color code of blue, yellow and red. To determine whether anomalous phenomena are precursors to the Tokai Earthquake, JMA convenes the Earthquake Assessment Committee for Areas under Intensified Measures against Earthquake Disaster ( 地震防災対策強化地域判定会), which consists of

seismologists Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

and members of

governmental organizations A government or state agency, sometimes an appointed commission, is a permanent or semi-permanent organization in the machinery of government that is responsible for the oversight and administration of specific functions, such as an administratio ...

. If the Committee concludes that the Tokai Earthquake is imminent, the Director-General of JMA will report this conclusion to the Prime Minister, who will then hold a Cabinet meeting and issue a warning statement ( 警戒宣言) .

Relation to other major earthquakes

The pattern of historical seismicity reveals that the megathrust surface is segmented, with five separate zones of rupturing identified, conventionally labeled A–E, from west to east. Earthquakes involving the A+B segments are generally referred to as Nankai (literally ''South Sea'') earthquakes, C+D Tōnankai (literally ''Southeast Sea'') earthquakes and E Tōkai (literally ''East Sea'') earthquakes. These earthquakes repeat at intervals generally in the range of 90 – 200 years. On all but one occasion, rupture of segment C (±D ±E) has been followed by rupture of segments A+B within a few years. This behavior has been reproduced by modeling the viscoelastic response of the megathrust fault plane with lateral variations in both convergence rate and frictional properties.

Historical Tōkai earthquakes

References

External links

Tokai earthquake information
from