1968 Tokachi earthquake
|UTC time||1968-05-16 00:49:02|
|Local date||May 16, 1968|
|Magnitude||8.3 Mw |
|Depth||26 km (16 mi) |
|Tsunami||6 m (20 ft) |
|Aftershocks||7.9 Mw (ISC) May 16 at 20:39|
|Casualties||47–52 killed  |
281–330 injured 
The 1968 Tokachi earthquake (1968年十勝沖地震 Sen-kyūhyaku-rokujūhachi-nen Tokachi-oki Jishin) occurred on May 16 at 0:49 UTC (09:49 local time) in the area offshore Aomori and Hokkaido. The magnitude of this earthquake was put at Mw 8.3. The intensity of the earthquake reached shindo 5 in Aomori, Aomori and Hakodate, Hokkaido.
This earthquake was located near the junction of the Kuril Trench and the Japan Trench. It is an interplate earthquake. The focal mechanism of this earthquake shows movement on a thrust fault with a considerable slip-strike component. The sum of interplate seismic moment release by seismic and aseismic faulting in this earthquake is about 28×1020 N m. The 1960s was noted as one of the peak periods of interplate seismic moment release in the offshore Sanriku region.
Heavy rain occurred due to a low pressure days before the earthquake and aggravated the damage. In Hokkaido, building damage was reported. A 4-story RC building of Hakodate University collapsed. In Aomori Prefecture, there was damage to railroads and highways in more than 200 places caused by collapses of artificial embankments. In Hachinohe, there was damage to buildings, water pipes, and gas pipes. The 3-story building of Hachinohe Technical College suffered severe damage. The communication between Honshu and Hokkaido was cut off.
A tsunami was triggered by the earthquake, with a maximum height of about 6 m (20 ft). A tsunami of 11 cm was recorded in Tahiti. In Japan, the tsunami caused flooding and damage to the aquaculture.
- USGS (September 4, 2009), PAGER-CAT Earthquake Catalog, Version 2008_06.1, United States Geological Survey
- Kanamori, H. (1971), "Focal Mechanism of the Tokachi-Oki Earthquake of May 16, 1968: Contortion of the Lithosphere at a Junction of Two Trenches", Tectonophysics, 12 (1): 1–13, Bibcode:1971Tectp..12....1K, doi:10.1016/0040-1951(71)90063-1
- Tsunami forecast Archives
- Hisashi Suito; Mikio Iizuka; Kazuro Hirahara (13 November 2003). "Crustal Deformation Model in Northeast Japan" (PDF). Archived from the original (PDF) on 2015-03-01. Retrieved 2014-09-12.
- "Space-time distribution of interplate moment release including slow earthquakes and the seismo-geodetic coupling in the Sanriku-oki region along the Japan trench" by I. Kawasaki, Y. Asai, and Y. Tamura
- Masaya HIROSAWA; Tomoaki AKIYAMA; Tatsuya KONDO & Jiandong ZHOU (16 December 1999). "DAMAGES TO BEAM-TO-COLUMN JOINT PANELS OF R/C BUILDINGS CAUSED BY THE 1995 HYOGO-KEN NANBU EARTHQUAKE AND THE ANALYSIS" (PDF). Retrieved 2014-09-12.
- "Geomorphological Accidents Caused by the Tokachi-oki Earthquake" by K. Nishimura, S. Segawa, H. Mizuno, H. Hotta, O. Miura, T. Tamura, and T. Akagiri
- Junji Kiyono (19 September 2008). "Earthquake and lifeline damage" (PDF). Archived from the original (PDF) on 2013-06-12. Retrieved 2014-09-12.
- "十勝沖地震 地震の概要". Bousai.pref.aomori.jp. Archived from the original on 2015-09-23. Retrieved 2014-09-12.
- 地震調査研究推進本部 地震調査委員会 (22 August 2008). "三陸沖から房総沖にかけての地震活動の長期評価の一部改訂について （平成21年3月9日公表）" (PDF). Retrieved 2014-09-12.
- [dead link]
- Izutani, Y. (2012), "Fault extent of the largest aftershock of the 1968 Tokachi-Oki, Japan, earthquake and an interpretation of the normal faulting focal mechanism", Earth, Planets and Space, 63 (12): 1213–1216, doi:10.5047/eps.2011.07.018