1968 Tokachi earthquake

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 of Aomori and Hokkaido. The magnitude of this earthquake was put at M_w 8.3.^[4] The intensity of the earthquake reached shindo 5 in Aomori, Aomori and Hakodate, Hokkaido.^[3]

1968 Tokachi earthquake

UTC time	1968-05-16 00:49:02
ISC event	821946
USGS-ANSS	ComCat
Local date	May 16, 1968 (1968-05-16)
Local time	09:49:02
Magnitude	8.3 Mw [1]
Depth	26 km (16 mi) [1]
Epicenter	40.90°N 143.35°E / 40.90; 143.35 [1]
Type	Oblique-slip
Areas affected	Japan
Max. intensity	MMI VI (Strong)[2] JMA 5−[3]
Tsunami	6 m (20 ft) [1]
Aftershocks	7.9 Mw(ISC)  May 16 at 20:39
Casualties	47–52 killed [1] 281–330 injured [1]

Geology

This earthquake was located near the junction of the Kuril Trench and the Japan Trench. It was an interplate earthquake.^[5] The focal mechanism of this earthquake showed movement on a thrust fault with a considerable slip-strike component.^[4] The sum of interplate seismic moment release by seismic and aseismic faulting in this earthquake was 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.^[6]

Damage

Heavy rain occurred due to a low pressure system in the days leading up to the earthquake and aggravated the damage. In Hokkaido, building damage was reported. A four-story RC building of Hakodate University collapsed.^[7] 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 three-story building of Hachinohe Technical College suffered severe damage.^[8] The communication between Honshu and Hokkaido was cut off.^[9]

Tsunami

A tsunami was triggered by the earthquake,^[10] with a maximum height of about 6 m (20 ft).^[11] An 11-centimeter (4.3 in) high tsunami was recorded in Tahiti.^[12] In Japan, the tsunami caused flooding and damage to aquaculture.^[10]

See also

• List of earthquakes in 1968
• List of earthquakes in Japan

References

1. USGS (September 4, 2009), PAGER-CAT Earthquake Catalog, Version 2008_06.1, United States Geological Survey
2. National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database, National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
3. "Tsunami forecast Archives" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2012-04-09.
4. 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
5. 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.
6. "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
7. 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.
8. "Geomorphological Accidents Caused by the Tokachi-oki Earthquake" by K. Nishimura, S. Segawa, H. Mizuno, H. Hotta, O. Miura, T. Tamura, and T. Akagiri
9. Junji Kiyono (19 September 2008). "Earthquake and lifeline damage" (PDF). Archived from the original (PDF) on 2013-06-12. Retrieved 2014-09-12.
10. "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.
11. 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.
12. ^{[dead link]}

Further reading

• 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" (PDF), Earth, Planets and Space, 63 (12): 1213–1216, doi:10.5047/eps.2011.07.018

External links

• The International Seismological Centre has a bibliography and/or authoritative data for this event.