  | |
| UTC time | ?? |
|---|---|
| Magnitude | at least 8 ML |
| Areas affected |  Japan: Tōkai region |
The Tokai earthquakes are earthquakes that have occured regularly with an interval of 100 to 150 years in the Tōkai region of Japan.
The whole country of Japan affected by earthquakes, but the most dangerous area of Japan is the coastal area just southwest of Tokyo on the island Honshū. In this area the Philippine plate is moving under the Eurasian plate. Japanese geologists have studied historical earthquake records, and mapped out segments of the area that seem to be affected repeatedly on a regular basis. This coastal area southwest of Tokyo, around Suruga Bay, is called the Tokai segment.
Last time a major earthquake affected the Tokai region was in 1854. Given the historic regularity the next earthquake is expected in the near futute. The Japanese government is taking the Tokai earthquakes seriously and has charged the Japan Meteorological Agency with the job of predicting the next one. They have 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 Tokai earthquake.
The anticipated Tokai earthquake is visualized in scenarios used by emergency planners. They need to create plans for an event that will likely thousands of deaths and injuries, and a million damaged buildings. It is expected to be at least magnitude 8 and large areas will be shaken at intensity 7, the highest level in the Japanese intensity scale. The magnitude is high so large damages are expected. But there is a lot of preparations in place.
Historical relation to other major earthquakes edit
The pattern of historical seismicity reveals that the megathrust surface is segmented, with five separate zones of rupturing identified, conventionally labelled A–E, from west to east.[1] Earthquakes involving the A+B segments are generally referred to as Nankai (literally South Sea) earthquakes, C+D Tonankai (literally Southeast Sea) earthquakes and E Tokai (literally East Sea) earthquakes. The earthquake repeat intervals are generally in the range 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 behaviour has been reproduced by modelling the viscoelastic response of the megathrust fault plane with lateral variations in both convergence rate and frictional properties.[1]
Historical Tokai earthquakes edit
| Date | Magnitude | Name | Death toll | Description |
|---|---|---|---|---|
| November 26, 684 | 8.3 | Hakuko earthquake | unknown | Landslides. Many houses, shrines and temples collapsed. |
| August 22, 887 | 8.5 | Ninna earthquake | unknown | Many people died in collapsing houses. |
| December 11, 1096 | 8.4 | Kowa earthquake | unknown | The main buidling of the imperial palace was damaged, and the the big bell of the Todai temple fell down. The tsunami in Suruga spilt houses, and 400 shrines and temples were damaged. |
| July 26, 1361 | 8.5 | Shohei earthquake | unknown | To be described. |
| September 11, 1498 | 8.4 | Meio earthquake | 40,000 | Kai haa a major shake. The buidling around great Buddha of Kamakura was swept away by the tsunami. In Minato Hiroshi 1,000 households was destroyed, 5,000 people drowned. 10,000 people drowned in Ise-Shima, in Shida District, Shizuoka Prefecture, 26,000 people died. Nankai earthquakes also occured around the same time according to the geological survey. |
| February 3, 1605 | 7.9 | Keicho earthquake | 2,300 | The tsunami attack from the Pacific coast of Kyushu, Miyazaki, led to that 57 people died in Hachijo Island, destroyed 700 houses in a village west of Kii wide, 1,500 people died in Shishikui Awa, Tosa Nishinoura 350 deaths, and 400 in the vicinity of Cape Muroto. |
| October 28, 1707 | 8.4 | Hoei earthquake | 20,000 | Tokai, Tonankai and Nankai earthquakes occurred at the same time with magnitude 8.4-8.6 (largest in Japanese history). Mt.Fuju erupted 49 days after this earthquake and the Hoei crater was created. About 20,000 people were killed and 60,000 houses collapsed, the Tosa area was affected by the tsunami. |
| December 23, 1854 | 8.4 | Ansei-Tokai earthquake | 3,000 | The epicenter ranged from Suruga Bay to the deep ocean, and struck primarily in the Tōkai region, but destroyed houses as far away as in Edo. The accompanying tsunami caused damage along the entire coast from the Bōsō Peninsula in modern-day Chiba prefecture to Tosa province (modern-day Kōchi prefecture).[2] |
See also edit
References edit
- ^ a b Hirahara, K. (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. Retrieved 2009-11-14.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ 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.