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April 2011 Fukushima earthquake

Coordinates: 37°00′25″N 140°28′37″E / 37.007°N 140.477°E / 37.007; 140.477
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April 2011 Fukushima earthquake
April 2011 Fukushima earthquake is located in Japan
April 2011 Fukushima earthquake
11 March quake
11 March quake
Tokyo
Tokyo
class=notpageimage|
Map showing the epicenter of the aftershock
UTC time??
Magnitude6.6 Mw[1]
Depth10 km (6 mi)
Epicenter37°00′25″N 140°28′37″E / 37.007°N 140.477°E / 37.007; 140.477
TypeAftershock
Areas affected Japan
Max. intensityMM VII[2]
TsunamiNo
LandslidesYes
Casualties6 confirmed dead, several injured[3]

The April 2011 Fukushima earthquake (福島県浜通り地震, Fukushima-ken Hamadōri jishin, lit. "Fukushima Hamadōri earthquake"[4]) was a potent magnitude 6.6 Mw intraplate aftershock that occurred at 17:16 JST (08:16 UTC) on Monday, 11 April 2011. With a shallow focal depth of 10 km (6 mi), it was centered inland about 36 km (22 mi) west of Iwaki, Japan, resulting in widespread moderate to localized strong shaking. The quake was one of many aftershocks to follow the 11 March Tōhoku earthquake, and the strongest to have its epicentre located inland.

The earthquake occurred as a result of normal faulting to the west of Iwaki, and triggered numerous landslides across adjacent mountainous areas. Few fires reportedly broke out, and some 220,000 households suffered power outages. Although localized tsunami alerts were issued, no significant waves were reported. There were no immediate reports of structural damage, but the quake killed six and injured several others.

USGS shake map

Geology

The magnitude 6.6 (Mw) earthquake occurred inland on 11 April 2011 at 08:16 UTC at a depth of 10 km (6 mi), about 36 km (22 mi) west of Iwaki, Fukushima, or 161 km (100 mi) north-northeast of Tokyo.[1] The quake resulted from normal faulting in the Hamadōri region along the active Idosawa Fault, which runs a length of 20 km (12 mi).[5] To the east, the oceanic Pacific Plate is being subducted beneath the continental Okhotsk Plate, leading to the formation of active inland faults near the resultant tectonic boundary.[6] Surveys held near the fault revealed a surface rupture of approximately 7 km (4 mi), with a right-lateral slip of about 30 cm (12 in) and vertical displacement of between 0.8 to 1.5 m (2.6 to 4.9 ft) reported at the lowering west side.[4] Early estimates placed the intensity of the tremor at a magnitude of 7.1 (Mw), but this was later revised to magnitude 6.6 by the USGS.[7] In addition, the Japan Meteorological Agency placed its intensity at a preliminary magnitude of 7.0.[8]

Although it was centered near a different fault zone, the earthquake was reported to be an aftershock of the 11 March Tōhoku earthquake, which occurred offshore about 235 km (145 mi) to its northeast.[9][1] The magnitude 9.0 earthquake triggered widespread seismic activity,[10] and its aftershock sequence includes well-over 58 earthquakes of magnitude 6.0 or greater.[11] Of the aftershocks, three registered higher than magnitude 7.0, with only one of them directly affecting land.[11] The Fukushima Hamadōri earthquake, however, was the strongest registered aftershock to have its epicentre located inland.[12]

Due to the very shallow focal depth of the quake, heavy shaking was reported in many adjacent areas; the strongest ground motion was registered in Ishikawa town at VII (very strong) on the Mercalli intensity scale. Strong shaking (MM VI) was also reported in Iwaki, Sukawaga, Kuroiso, Ōtawara, and Kitaibaraki, with light tremors (MM IV) felt in areas up to several hundred kilometres from the epicentre, including Tokyo and Yokohama.[2]

The quake was succeeded by a number of smaller tremors; that same day, at least 11 earthquakes of over magnitude 3.5 were reported near its epicenter.[13] Of the series, the strongest registered at a magnitude of 5.5 (Mw), and occurred within 3.5 hours after the initial quake.[14]

Impact

The earthquake struck during the morning near a moderately populated region; however, most structures around the epicentre were reported to be resistant to earthquake shaking.[2] About 220,000 households reportedly lost power, with most outages occurring in Iwaki city.[15] Workers at the Fukushima Daiichi power plant — distanced near 70 km (40 mi) from the epicentre[16][1] — evacuated to safety, while external power to the plant was cut off. The outage briefly disrupted cooling water injections into three of its reactors, though power service was restored by 18:05 local time.[17] Authorities at Tokyo International Airport were forced to close all runways momentarily,[18] while voice calls following the quake were restricted by NTT DoCoMo in 14 prefectures. East Japan Railway Company temporarily suspended its services to restart four of five bullet-train lines; Shinkansen bullet trains in the region were also halted.[15][17]

The tremor sparked several fires in Iwaki, with one fire breaking out in Asakawa town. Fire trucks extinguished a lightning-induced fire in a liquefied natural gas tank at Daiichi Sankyo's Onahama Plant.[15] Landslides triggered by the quake crushed two vehicles[15] and buried three homes in Iwaki, trapping a number of the inhabitants. Initially, four people were estimated to be trapped, but officials later reported more victims. The incident resulted in at least six confirmed deaths, and three others were rescued and immediately hospitalized.[3] An additional five injuries were reported in surrounding locations, including southern Ibaraki, Kitaibaraki, Hiratsuka, and Shioya town.[19]

Response

In response to the tremor, Prime Minister Naoto Kan postponed a press conference scheduled for 17:50 local time to mark the one-month anniversary of the 11 March Tōhoku earthquake and tsunami, which left copious amounts of devastation in its wake. At the threat of a tsunami — which reach dangerous wave heights near shallow coastal waters[20] — local fishing boats along coastlines were shown heading out to sea on national news broadcasts.[15] A warning for a localized tsunami of up to 2.0 m (6.6 ft) was issued by the Japan Meteorological Agency; however, no waves were reported, and the warning was later canceled.[21][15] The earthquake occurred in a historically seismically inactive region; studies indicated activity near the fault zone was triggered by the Tōhoku quake.[4] According to Professor Yagi Hiroshi from the Faculty of Education, Art and Science, "a possibility exists for widespread aftershocks of the same size to occur in the near future."[5]

See also

References

  1. ^ a b c d "Magnitude 6.6 – Eastern Honshu, Japan". earthquake.usgs.gov. USGS. 11 April, 2011. Retrieved 2011-04-22. {{cite web}}: Check date values in: |date= (help)
  2. ^ a b c "Pager - M 6.6 – Eastern Honshu, Japan". earthquake.usgs.gov. USGS. 11 April, 2011. Retrieved 2011-04-22. {{cite web}}: Check date values in: |date= (help)
  3. ^ a b CNN Wire Staff (11 April, 2011). "At least 6 killed in new Japan earthquake". articles.cnn.com. CNN World News. Retrieved 2011-04-23. {{cite web}}: |author= has generic name (help); Check date values in: |date= (help)
  4. ^ a b c Template:Ja "2011年4月11日の福島県浜通りの地震に伴う地表地震断層について". outreach.eri.u-tokyo.ac.jp. Outreach and Public Relations Office. 13 April, 2011. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help)
  5. ^ a b Template:Ja "いわき市の地表に７キロの断層　４月１１日の余震でずれ". asahi.com. Asahi Shimbun Company. 13 April, 2011. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help)
  6. ^ Template:Ja "先日のＭ７余震、予想外の井戸沢断層が原因". yomiuri.co.jp. Yomiuri Shimbun Online. 16 April, 2011. Retrieved 2011-05-02. {{cite web}}: Check date values in: |date= (help)
  7. ^ AFP (11 April, 2011). "Japan rattled by 6.6 aftershock". theage.com.au. The Age. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help)
  8. ^ Template:Ja "福島県浜通りの地震について" (PDF). jma-net.go.jp. Sendai District Meteorological Observatory. 11 April, 2011. Retrieved 2011-05-02. {{cite web}}: Check date values in: |date= (help); External link in |publisher= (help)
  9. ^ "Magnitude 9.0 - near the East Coast of Honshu, Japan". earthquake.usgs.gov. USGS. 11 March, 2011. Retrieved 2011-04-28. {{cite web}}: Check date values in: |date= (help)
  10. ^ Choi, Charles Q (19 April, 2011). "Japan earthquake triggered smaller quakes around the world". msnbc.com. MSNBC. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help)
  11. ^ a b "Magnitude 7.1 – near the East Coast of Honshu, Japan". earthquake.usgs.gov. USGS. 11 April, 2011. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help)
  12. ^ "2011 Significant Earthquake and News Headlines Archive". earthquake.usgs.gov. USGS. 2011. Retrieved 27 April, 2011. {{cite web}}: Check date values in: |accessdate= (help)
  13. ^ "Earthquake Information 2011/04 (UT)". fnet.bosai.go.jp. NIED. April 2011. Retrieved 2011-04-23. {{cite web}}: External link in |publisher= (help)
  14. ^ "Event – 36.9N 140.6E, 8km Mw5.5". fnet.bosai.go.jp. NIED. 11 April, 2011. Retrieved 2011-04-23. {{cite web}}: Check date values in: |date= (help); External link in |publisher= (help)
  15. ^ a b c d e f Wei, Teo Chian/Reidy, Gearoid (23 April, 2011). "Magnitude-6.6 quake hits Japan near stricken nuclear power plant". Bloomberg L.P. Retrieved 2011-03-23. {{cite web}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  16. ^ "Fukushima Daiichi Nuclear Power Plant - 1–4 unites - Japan". tageo.com. Tageo.com. Retrieved 2011-04-28.
  17. ^ a b Boyd, John (11 April, 2011). "Quake and tsunami warning halt work at Fukushima Plant". spectrum.ieee.org. IEEE Spectrum. Retrieved 2011-04-27. {{cite web}}: Check date values in: |date= (help)
  18. ^ Associated Press (11 April, 2011). "7.1 magnitude earthquake shakes northeast Japan". abcactionnews.com. ABC Action News. Retrieved 2011-04-26. {{cite web}}: Check date values in: |date= (help)
  19. ^ Template:Ja Vervaeck, Armand/Daniel, James (12 April, 2011). "3 人は大きさのために殺される 6.6 余震 (東本州, 日本)". earthquake-report.com. 地震- Report. Retrieved 2011-04-25. {{cite web}}: Check date values in: |date= (help)CS1 maint: multiple names: authors list (link)
  20. ^ "Life of a Tsunami". Western Coastal & Marine Geology. USGS. 22 October, 2008. Retrieved 2011-04-27. {{cite web}}: Check date values in: |date= (help)
  21. ^ Staff Writer (11 April, 2011). "Japan hit by 6.6 magnitude earthquake". rte.ie. RTÉ News. Retrieved 2011-03-23. {{cite web}}: Check date values in: |date= (help)

External links

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