Tōkai earthquakes
The Tōkai earthquakes (Japanese: 東海地震) are major earthquakes that have occurred regularly with a return period of 100 to 150 years in the Tōkai region of Japan. The Tōkai segment has been struck by earthquakes in 1498, 1605, 1707, and 1854.[1] Given the historic regularity of these earthquakes, Kiyoo Mogi in 1969 pointed out that another great shallow earthquake was possible in the "near future" (i.e., in the next few decades).[2]
Given the magnitude of the last two earthquakes, the next is expected to have at least a magnitude scale of 8.0
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
Earthquake prediction
The Tokai Earthquake is expected to occur in the near future along the trench near Suruga Bay 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.[5]
The Japanese government is taking the Tōkai earthquakes seriously and has charged the Japan Meteorological Agency 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
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.[5]
Information on future quakes is published irregularly.[6][7][8] 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.[9][10][11]
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 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.[5]
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.[5] 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.[5]
| Information issued by JMA | Announcement timing | Action to be taken by the general public | Action to be taken by public organizations |
|---|---|---|---|
| Explanatory Information on Tokai Earthquake Warning 東海地震予知情報 |
When it is considered that the Tokai Earthquake may occur and the prime minister issues a warning declaration (警戒宣言) .[5] | Response warning declaration from the prime minister and local-government disaster management plans. | Establishment of Headquarters for Earthquake Disaster Prevention |
| Tokai Earthquake Watch 東海地震注意情報 |
When there is increased likelihood that an observed phenomenon is a precursor to the Tokai Earthquake.[5] | Response to notification from the government and local-government disaster management plans.[5] | Preparatory action based on prevention plans |
| Investigation Report on Tokai Earthquake (Extra) 東海地震に関連する調査情報 (臨時) |
When any anomalous phenomena are observed. | No further action required. | Collection of Information |
| Investigation Report on Tokai Earthquake (Regular) 東海地震に関連する調査情報 (定例) |
When the Earthquake Assessment Committee (Regular) meets. | No further action required. | None |
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 (
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.[12] 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.[12]
Historical Tōkai earthquakes
| Date | Magnitude
|
Name | Death toll | Description | Years since previous earthquake |
|---|---|---|---|---|---|
| November 26, 684 | 8.3 | Hakuhō earthquake |
unknown | Landslides. Many houses, shrines and temples collapsed. | No records |
| August 22, 887 | 8.5 | Ninna earthquake | unknown | Many people were killed by collapsing houses. | 203 |
| December 11, 1096 | 8.4 | Kōwa earthquake | unknown | The main building of the imperial palace was damaged, and the big bell of the Tōdai-ji temple fell down. The tsunami in Suruga split houses, and 400 shrines and temples were damaged. | 209 |
| July 26, 1361 | 8.5 | Shohei earthquake | unknown | Considerable damage. | 265 |
| September 11, 1498 | 8.4 | Meiō earthquake |
40,000 | Kai was severely shaken. The buildings around the great Buddha of Kamakura (altitude 7m) were swept away by a tsunami. In Ōminato, Ise 1,000 households were destroyed with 5,000 people drowned. 10,000 people drowned in Ise-Shima, while in Shida District, Shizuoka Prefecture, 26,000 people died. Nankai earthquakes also occurred around the same time, according to the Geological Survey of Japan. | 137 |
| February 3, 1605 | 7.9 | 1605 Keichō Nankaidō earthquake |
2,300 | The tsunami struck from the Pacific coast of Kyushu, Miyazaki, led to the deaths of 57 on the island Hachijō-jima, destroyed 700 houses in a village west of the Kii Peninsula, 1,500 people died in Shishikui Awa, 350 deaths in Tosa Nishinoura, and 400 in the vicinity of Cape Muroto. | 107 |
| October 28, 1707 | 8.4 | Hoei earthquake | 20,000 | Tōkai, Tōnankai and Nankai earthquakes occurred at the same time with magnitude 8.4–8.6. Mount Fuji erupted 49 days after this earthquake and the Hōei crater was created. About 20,000 people were killed and 60,000 houses collapsed, the Tosa area was affected by the tsunami. | 102 |
| December 23, 1854 | 8.4 | Ansei-Tōkai earthquake |
3,000 | The Tosa province (modern-day Kōchi Prefecture).[13] |
147 |
See also
- 1944 Tōnankai earthquake
- Coordinating Committee for Earthquake Prediction
- Kanto earthquakes
- List of earthquakes in Japan
- Nankai megathrust earthquakes
References
- About.com. Archived from the originalon February 24, 2012. Retrieved May 19, 2012.
- ^ a b c d Kiyoo Mogi (2004). "Two grave issues concerning the expected Tokai Earthquake" (PDF). Earth Planets Space. 56 (8): li–lxvi. Retrieved March 11, 2011.
- Mercalli intensity scale
- The Huffington Post. Retrieved May 19, 2012.
- ^ a b c d e f g h i j Information on the Tokai Earthquake - JMA
- ^ 気象庁が発表する「東海地震に関連する情報」 - JMA
- ^ "気象庁｜東海地震について | 東海地震に関連する情報". 2014-03-18. Archived from the original on 2014-03-18. Retrieved 2021-05-02.
- ^ "気象庁｜東海地震について | 東海地震に関連する情報の種類と流れ". 2014-03-18. Archived from the original on 2014-03-18. Retrieved 2021-05-02.
- ^ 南海トラフ地震について 気象庁
- ^ 「南海トラフ地震に関連する情報」の発表について 気象庁報道発表資料（2017年9月26日）
- ^ "気象庁｜東海地震について". www.data.jma.go.jp. Retrieved 2021-05-02.
- ^ a b Hirahara, K.; Kato N.; Miyatake T.; Hori T.; Hyodo M.; Inn J.; Mitsui N.; Sasaki T.; Miyamura T.; Nakama Y.; Kanai T. (2004). "Simulation of Earthquake Generation Process in a Complex System of Faults" (PDF). Annual Report of the Earth Simulator Center April 2004 - March 2005. pp. 121–126. Archived from the original (PDF) on 2011-09-27. Retrieved 2009-11-14.
- ^ Kawade Shobō Shinsha Editorial Team (eds.). "Ansei Daijishin" (安政大地震, "Great Earthquakes of Ansei"). Ō-Edo Rekishi Hyakka (大江戸歴史百科, "Historical Encyclopedia of Great Edo"). Tokyo: Kawade Shobō Shinsha Publishers, 2007. p253.