2007 Chūetsu offshore earthquake

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Coordinates: 37°57′N 138°44′E / 37.950°N 138.733°E / 37.950; 138.733

2007 Chūetsu Offshore Earthquake
Japan quake July 16.2007.jpg
Date July 16, 2007 (2007-07-16)
Magnitude 6.6 Mw
Depth 10km
Areas affected Japan
Peak acceleration 1.01 g
Casualties 11 dead, over 1120 injured

The Chūetsu Offshore Earthquake (Japanese: 平成19 年(2007 年)新潟県中越沖地震[1]) was a powerful magnitude 6.6 earthquake[2][3] that occurred 10:13 a.m. local time (01:13 UTC) on July 16, 2007, in the northwest Niigata region of Japan. The earthquake, which occurred at a previously unknown offshore fault[4] shook Niigata and neighbouring prefectures. The city of Kashiwazaki and the villages of Iizuna and Kariwa registered the highest seismic intensity of a strong 6 on Japan's shindo scale, and the quake was felt as far away as Tokyo.[2] Eleven deaths and at least 1000 injuries were reported, and 342 buildings were completely destroyed, mostly older wooden structures.[2][5][6]

Prime Minister Shinzō Abe broke off from his election campaign in Southern Japan to visit Kashiwazaki and promised to "make every effort towards rescue and also to restore services such as gas and electricity".[7]

Tectonic summary[edit]

Sidewalk of Higashi-honcho, Kashiwazaki
The landslide of Ōmigawa Station (July 2007)

This magnitude 6.6 earthquake occurred approximately 15 miles off the west coast of Honshū, Japan, in a zone of compressional deformation that is associated with the boundary between the Amur plate and the Okhotsk plate. At this latitude, the Okhotsk Plate is converging to the west-northwest towards the Amur Plate with a velocity of about 9 mm/yr and a maximum convergence rate of 24 mm/yr.[8] The Amur and Okhotsk plate are themselves relatively small plates that lie between the Eurasian Plate and the Pacific Plate. The Pacific plate converges west-northwest towards the Eurasia plate at over 90 mm/yr. Most of the relative motion between the Pacific plate and the Eurasia plate is accommodated approximately 400 km to the east-southeast of the epicenter of the earthquake, where the Pacific plate subducts beneath the Okhotsk plate.

This shallow crustal earthquake was followed 13 hours later by a deep focus magnitude 6.8 quake roughly 330 km to the west, 350 km below the Sea of Japan. The two earthquakes were generated by different mechanisms. The first earthquake was caused by deformation within the crust of the Okhotsk plate and the second quake was likely caused by faulting resulting from internal deformation of the subducted Pacific plate. Given their different mechanisms and physical separation of at least 10 rupture lengths, the second earthquake is not considered an aftershock of the first.

Shallow earthquakes cause more damage than intermediate- and deep-focus ones since the energy generated by the shallow events is released closer to the surface and therefore produces stronger shaking than is produced by quakes that are deeper within the Earth.[9][10] The peak ground acceleration generated was 993 gal (1.01 g).[11]

Two days after the initial earthquake, an aftershock occurred, registering 4 shindo in Izumozaki, Niigata[12]

Automotive production[edit]

Toyota motor announced it stopped production in all of its factories because of the damage done to the Riken parts plant in Kashiwazaki, Niigata. Nissan also had to shut down two factories.[13] Furthermore, Tanigawa-Shaitoyama automobiles permanently shut down their automobile production due to huge losses. [14]

Production resumed in Toyota, Mazda, and Honda plants on July 25, after damaged equipment and gas and water supplies were restored. Toyota's production losses amounted to between 46,000 or possibly 55,000 vehicles. Nissan lossed 12,000 vehicles.[15]

Kashiwazaki-Kariwa Nuclear Power Plant incidents[edit]

The earthquake caused a leak of radioactive gases from Kashiwazaki-Kariwa Nuclear Power Plant. A small amount of water from the spent fuel pool leaked out but plant operators said the leak was low and did not present any environmental danger.[2][6] The earthquake also caused a fire in an electrical transformer at the Kashiwazaki-Kariwa Nuclear Power Plant that was extinguished after two hours.

The government requested that the plant remain closed pending safety inspections. The IAEA offered to send a team of experts to inspect the plant.[16] The Japanese government initially declined the offer but later accepted it after Niigata Prefecture legislature asked for confidence building efforts to counter public concern about the reactor.[17]

The area was hard hit by tourist cancellations due to fears relating to the plant.

Following the incident Dr Kiyoo Mogi, chair of Japan's Coordinating Committee for Earthquake Prediction, called for the immediate closure of the Hamaoka Nuclear Power Plant, which was built close to the centre of the expected Tōkai earthquake.[18][19]

See also[edit]

Sources[edit]

  1. ^ "2007 年7月16 日10 時13 分ころ新潟県上中越沖で発生した地震について". Japan Meteorological Agency. July 16, 2007. Retrieved July 19, 2007.  (Japanese)
  2. ^ a b c d "Powerful earthquake strikes Niigata, causes leak at nuclear power plant". Japan News Review. July 16, 2007. Retrieved 16 July 2007. 
  3. ^ asahi.com:新潟、長野で震度6強 8人死亡、908人がけが – 社会[dead link]
  4. ^ Alex K. Tang, PE and Anshel J. Schiff (ed.). Kashiwazaki, Japan Earthquake of July 16, 2007. Reston, VA: ASCE, Technical Council on Lifeline Earthquake Engineering. p. 11. ISBN 9780784410622. 
  5. ^ Niigata earthquake death toll rises to eleven Japan News Review, July 23
  6. ^ a b "Japanese nuke plant leaked after earthquake". Associated Press. July 16, 2007. Archived from the original on August 10, 2007. Retrieved July 16, 2007. 
  7. ^ "Nuclear scare after Japan quake". BBC. July 16, 2007. Archived from the original on 23 August 2007. Retrieved July 16, 2007. 
  8. ^ Alex K. Tang, PE and Anshel J. Schiff, ed. (2007). "2". Kashiwazaki, Japan Earthquake of July 16, 2007. ASCE, Technical Council on Lifeline Earthquake Engineering. p. 7. ISBN 9780784410622. 
  9. ^ Magnitude 6.6 – NEAR THE WEST COAST OF HONSHU, JAPAN
  10. ^ "Aftershock strikes Niigata Pref.". Mainichi Daily News. July 16, 2007. Retrieved 16 July 2007. 
  11. ^ Katsuhiko, Ishibashi (August 11, 2001). "Why Worry? Japan's Nuclear Plants at Grave Risk From Quake Damage". Japan Focus (Asia Pacific Journal). Archived from the original on March 15, 2011. Retrieved March 15, 2011. 
  12. ^ Aftershock hits Niigata – Japan News Review
  13. ^ USA Today. Earthquake puts brakes on auto production in Japan,
  14. ^ Japango Sahtano. Impact of the Chuetsu earthquake on small automobile industries (2007)
  15. ^ Caranddriver.com. Japan's Auto Plants Reopen After Earthquake Shutdown – Daily Auto Insider. July 25.
  16. ^ IAEA Offers to Send Expert Team to Japan Following Earthquake
  17. ^ Japan accepts IAEA inspectors after quake troubles
  18. ^ Quake shuts world's largest nuclear plant Nature, vol 448, 392–393, doi:10.1038/448392a, published 2007-07-25. Retrieved March 18, 2011.
  19. ^ Nuclear crisis in Japan as scientists reveal quake threat to power plants The Times, published 2007-07-19. Retrieved March 18, 2011.

 This article incorporates public domain material from websites or documents of the United States Geological Survey.