1982 Urakawa earthquake

The 1982 Urakawa earthquake (Japanese: 浦河沖地震[6]) was a Mw 6.9 earthquake that struck off the coast of Urakawa, Japan on 11:32 (JST), March 21, 1982.[7][8][9] The epicenter was 42.1°N 142.6°E / 42.1; 142.6.[10] The earthquake was the largest earthquake in the history of the region. The earthquake caused 167 injuries and damage in Tomakomai and Sapporo.[11][12]

1982 Urakawa earthquake
1982 Urakawa earthquake is located in Hokkaido
1982 Urakawa earthquake
1982 Urakawa earthquake is located in Japan
1982 Urakawa earthquake
UTC time1982-03-21 02:32:07
ISC event602579
USGS-ANSSComCat
Local dateMarch 21, 1982 (1982-03-21)
Local time11:32
Magnitude6.7–6.8 Ms[1][2]
6.9 Mw[3]
7.1 MJMA
Depth44.0 km (27.3 mi)
Epicenter42.158°N 142.361°E / 42.158; 142.361
Areas affectedJapan
Total damage$1 million USD[4]
Max. intensityJMA 6−
X (Extreme)[4]
Tsunami1.3 m (4.3 ft)[4]
ForeshocksYes
AftershocksYes, largest Mw  5.9[5]
Casualties167 injured[4]

Tectonic setting

Hokkaido is situated on the Okhotsk Plate in between two main zones of seismicity. To the west, there is a convergent plate boundary with the Amurian Plate.[13] To the east, there exists a subduction zone where the Pacific Plate subducts underneath the Okhotsk. This is accommodated by slip along the Kuril-Kamchatka Trench and the Japan Trench.[14] This earthquake struck as the result of thrust faulting in an area of compression known as the Hidaka Collision Zone.[15] The same tectonic process, caused by the collision between the Eurasian Plate and the Kuril fore-arc uplifts the Hidaka Mountains.[15]

Earthquake

At 2:32 UTC or 11:32 local time on the 21st of March, a large earthquake struck off the shore of southern Hokkaido. The Mw 6.9 earthquake caused shaking that reached a maximum Japan Meteorological Agency seismic intensity scale Shindo of 6- and a Modified Mercalli intensity (MMI) of X (Extreme). The event struck at a depth of 44.0 km (27.3 mi), and ruptured along the Hidaka Collision Zone.[15] Inferred rupture dimensions were 12 km (7.5 mi) by 22 km (14 mi) with an average slip of 2.5 m (8 ft 2 in).[5] Aftershocks covered an area of 35 km (22 mi) by 25 km (16 mi).[9]

Tsunami
Teletsunami observations[16]
LocationRecorded height (m)
Urakawa, Japan1.3
Ayukawa, Japan0.6
Hachinohe, Japan0.6
Shoya, Japan0.3
Kuji, Japan0.3
Kamaishi, Japan0.2
Kushiro, Japan0.2

Tsunami from the earthquake was observed around Hokkaido, with varying run-up heights.[16] Urakawa had the highest run-ups with waves reaching up to 1.3 m (4 ft 3 in) high and going up to 3 m (9.8 ft) inland.[16] The observations at Hachinohe and Hiroo were much higher than models predicted, however this may be due to the models not taking into account more local topography that could influence wave heights.[5]

References
  1. "M 6.7 - 19 km S of Shizunai-furukawach?, Japan". earthquake.usgs.gov. United States Geological Survey. Retrieved 23 May 2022.
  2. Murai et al. 2003.
  3. International Seismological Centre. ISC-GEM Global Instrumental Earthquake Catalogue. Thatcham, United Kingdom. [Event 602579].
  4. "Event:HOKKAIDO, JAPAN". ngdc.noaa.gov.
  5. Suetsugu & Nakanishi 1988.
  6. "気象庁 | 気象庁が名称を定めた気象・地震・火山現象一覧". www.jma.go.jp. Retrieved 2021-06-29.
  7. デジタル大辞泉. "浦河沖地震とは". コトバンク (in Japanese). Retrieved 2021-06-29.
  8. "1982年浦河沖地震港湾被害報告". www.pari.go.jp. Archived from the original on 2021-06-02. Retrieved 2021-06-29.
  9. Iwasaki et al. 1983.
  10. "20世紀後半（1951-）｜日本付近のおもな被害地震年代表｜公益社団法人 日本地震学会". www.zisin.jp. Retrieved 2021-06-29.
  11. "The Earthquake off Urakawa (M 7.1), March 21, 1982" (PDF) (in Japanese). Hokkaido University. Retrieved 3 December 2018.
  12. "浦河沖地震（1982年3月21日） ｜ 災害カレンダー". Yahoo!天気・災害 (in Japanese). Retrieved 2021-06-29.
  13. Zhou et al. 2011.
  14. Seno, Sakurai & Stein 1996.
  15. Arita et al. 1998.
  16. Lander, James F.; Whiteside, Lowell S.; Lockridge, Patricia A. "TWO DECADES OF GLOBAL TSUNAMIS 1982-2002" (PDF). NOAA. Retrieved 30 October 2022.

Sources


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