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Seismicity of the Sanriku coast

April 09, 2024

See also: Sanriku earthquake

The seismicity of the Sanriku coast identifies and describes the seismic activity of an area of Japan. Seismicity refers to the frequency, type and size of earthquakes experienced over a period of time. The Sanriku Coast (三陸海岸, Sanriku kaigan) is a descriptive term referring to the coastal areas of the former provinces of Rikuō in Aomori, Rikuchū in Aomori, and Rikuzen in Miyagi.[2]

Historical tsunamis in the Sanriku area and selection of areas affected by the 2011 Tōhoku tsunami
Seismic regions around the East Japan Megathrust designated by the Headquarters for Earthquake Research Promotion[1]

The irregular ria coastline and its many bays tend to amplify the destructiveness of tsunami waves which reach the shores of Sanriku,[3] as demonstrated in the damage caused by the 2011 Tōhoku earthquake and tsunami.

History edit

The Sanriku coast has a well-documented history of significant seismic activity. A major earthquake in the 19th century caused more than 20,000 deaths, and another in the 20th century caused thousands more. The recurrence of major seismic activity continues in the 21st century.

Ancient edit

There is geological evidence[4][5] of six catastrophic tsunamis hitting the Sanriku coast within 6000 years. Among them are:

19th century edit

Some 22,000 people were killed in the Meiji Sanriku earthquake of 1896. Most of the deaths were caused by tsunami. The disaster struck at 7:32 pm on the afternoon of June 15.[6] The epicenter was determined to have been located at 39.5 Latitude/140.6 Longitude, and the earthquake had an estimated magnitude of Mw8.5 .[7]

20th century edit

Major seismic activity on the Sanriku coast during the 20th century includes:

21st century edit

Significant seismic events which devastated Sanriku coastal communities in the 21st century include:

  • 2003 Miyagi earthquake. There were two major earthquakes in 2003 in Miyagi Prefecture. The first quake in May injured 171 and caused $97.3 million in damage.[11] Another quake in July injured 676. More than 11,000 buildings were affected, causing an estimated $195.4 million in damage.[12]
  • 2005 Miyagi earthquake. The seismic event was originally recorded by the United States Geological Survey as a 7.2-magnitude earthquake on the Moment magnitude scale, but the Japan Meteorological Agency called it a magnitude 6.9 earthquake. The slippage in the seabed subduction zone was located about 330 miles (530 kilometres) east-northeast of Tokyo about 24 miles (39 kilometres) below the surface of the Pacific Ocean. The Japan Meteorological Agency issued a tsunami warning almost immediately; and warnings were also issued for the northwest coast of the United States
  • 2011 Tōhoku earthquake and tsunami. In March 2011, the largest earthquake ever recorded in Japan struck off the Sanriku coast, setting off a 10 metres (33 feet) tsunami. The 9.0-magnitude quake near Tohoku was comparable in scale to undersea seismic events near Indonesia in 2004 (3rd largest on record) and near Chile in 2010 (6th largest).[13] It caused 15,889 deaths, 6,152 injured, and 2,609 people missing across twenty prefectures, with an estimated $235 billion in property damage.

In the list of 45 most powerful earthquakes recorded worldwide since 1500, there are five that appear to be clustered in a 8-year span (in 2004, 2005, 2010, 2011, 2012) with the largest being the 2004 Indian Ocean earthquake of magnitude 9.1. Prior to this, no sizable earthquake occurred. There was another apparent cluster (in 1960, 1963, 1964, 1965) which contained the largest recorded earthquake, the 1960 Valdivia earthquake of magnitude 9.4. However, experts construe this as a statistical anomaly or random chance.[13][14]

The phenomenon of comparably large quakes that happen on the same or neighbouring faults within months of each other—for example, the Miyagi quakes in 2003—can be explained by a sound geological mechanism. This does not fully demonstrate a relationship between events separated by longer periods and greater distances.[14]

Seismic mechanisms edit

Earthquakes occur where the Pacific Plate meets the plate beneath northern Honshu in a subduction zone.[15] The Pacific plate, which moves at a rate of 8 to 9 cm (3.1 to 3.5 in) per year, dips under Honshu's underlying plate releasing large amounts of energy. This motion pulls the upper plate down until the stress builds up enough to cause a seismic event.

Quakes of large magnitudes in the Sanriku region can have a rupture length of hundreds of kilometers; and this generally requires a long, relatively straight fault surface. However, the plate boundary and subduction zone in this area is not very straight.[16] The "epicentral region" of an earthquake is defined as an elliptical area which encompasses the location of highest felt intensity of an earthquake. This term is used for identifying the likely epicenter for earthquakes and tsunami in the history of the Sanriku coat.

The hypocentral region of Sanriku coastal earthquakes can occur in locations extending from offshore Aomori Prefecture to offshore Ibaraki Prefecture.

See also edit

Notes edit

 
Wikinews has related news:
  • Quake measuring 6.9 off Japan's Honshū coast
  1. ^ "Evaluation of Major Subduction-zone Earthquake". Headquarters for Earthquake Research Promotion. 2008. from the original on 8 March 2022. Retrieved 17 March 2022.
  2. ^ Saw-tooth Sanriku Coastline (三陸リアス式海岸, Sanriku-riasushiki-kaigan) at Nippon-Kichi
  3. ^ Satake, Kenji (2005). Tsunamis: Case Studies and Recent Developments. Advances in Natural and Technological Hazards Research (Book 23). Springer. p. 99. Bibcode:2005tcsr.book.....S. ISBN 978-1402033261.
  4. ^ . Archived from the original on 2011-08-24. Retrieved 2011-09-04.
  5. ^ Minoura, Koji (30 June 2001). 津波災害は繰り返す (in Japanese). Tohoku University. Retrieved 14 March 2011.
  6. ^ Online "NOAA/Japan: Significant Earthquake Database," U.S. National Oceanic and Atmospheric Administration (NOAA), National Geophysical Data Center (NGDC)
  7. ^ Nishimura, T.; Miura S.; Tachibana K.; Hashimoto K.; Sato T.; Hori S.; Murakami E.; Kono T.; Nid K.; Mishina M.; Hirasawa T. & Miyazaki S. (2000). "Distribution of seismic coupling on the subducting plate boundary in northeastern Japan inferred from GPS observations". Tectonophysics. 323 (3–4): 217–238. Bibcode:2000Tectp.323..217N. doi:10.1016/S0040-1951(00)00108-6.
  8. ^ USGS. . Archived from the original on 23 January 2010. Retrieved 6 July 2010.
  9. ^ Sidle, R.C. et al. (1985). Hillslope stability and land use, pp. 1–9., p. 1, at Google Books
  10. ^ Nakayama and Takeo. "Slip history of the 1994 Sanriku-Haruka-Oki, Japan, earthquake deduced from strong-motion data," Bulletin of the Seismological Society of America, Vol. 87, No. 4, p. 918.
  11. ^ Disaster Control Research Center, Tohoku University: May 26, 2003 Miyagi-Oki earthquake Archived September 7, 2012, at archive.today
  12. ^ Disaster Control Research Center: July 26, 2003 Northern Miyagi earthquake Archived August 4, 2012, at archive.today
  13. ^ a b Pappas, Stephanie. "Sumatra, Japan, Chile: Are Earthquakes Getting Worse?" LiveScience, 11 March 2011.
  14. ^ a b Brahic, Catherine. "The megaquake connection: Are huge earthquakes linked?" New Scientist (UK), 16 March 2011.
  15. ^ Sample, Ian. "Japan earthquake and tsunami: what happened and why," The Guardian (UK). 11 March 2011; retrieved 14 Mar 2011
  16. ^ Maugh, Thomas H. "Size of Japan's quake surprises seismologists," Los Angeles Times (US). 11 March 2011; retrieved 11 Mar 2011

References edit

  • Sidle, R.C.; Pearce, A.J.; O'Loughlin, C.L. (1985) Hillslope stability and land use. Washington, D.C.: American Geophysical Union. ISBN 978-0-87590-315-6

External links edit

April 09, 2024
seismicity, sanriku, coast, also, sanriku, earthquake, seismicity, sanriku, coast, identifies, describes, seismic, activity, area, japan, seismicity, refers, frequency, type, size, earthquakes, experienced, over, period, time, sanriku, coast, 三陸海岸, sanriku, ka. See also Sanriku earthquake The seismicity of the Sanriku coast identifies and describes the seismic activity of an area of Japan Seismicity refers to the frequency type and size of earthquakes experienced over a period of time The Sanriku Coast 三陸海岸 Sanriku kaigan is a descriptive term referring to the coastal areas of the former provinces of Rikuō in Aomori Rikuchu in Aomori and Rikuzen in Miyagi 2 Historical tsunamis in the Sanriku area and selection of areas affected by the 2011 Tōhoku tsunamiSeismic regions around the East Japan Megathrust designated by the Headquarters for Earthquake Research Promotion 1 The irregular ria coastline and its many bays tend to amplify the destructiveness of tsunami waves which reach the shores of Sanriku 3 as demonstrated in the damage caused by the 2011 Tōhoku earthquake and tsunami Contents 1 History 2 Ancient 2 1 19th century 2 2 20th century 2 3 21st century 3 Seismic mechanisms 4 See also 5 Notes 6 References 7 External linksHistory editThe Sanriku coast has a well documented history of significant seismic activity A major earthquake in the 19th century caused more than 20 000 deaths and another in the 20th century caused thousands more The recurrence of major seismic activity continues in the 21st century Ancient editThere is geological evidence 4 5 of six catastrophic tsunamis hitting the Sanriku coast within 6000 years Among them are A catastrophic tsunami about 5400 6000 years ago predating the Towada eruption A catastrophic tsunami about 2000 years ago 869 AD Jogan earthquake and tsunami 1611 AD Keicho Sanriku earthquake 19th century edit Some 22 000 people were killed in the Meiji Sanriku earthquake of 1896 Most of the deaths were caused by tsunami The disaster struck at 7 32 pm on the afternoon of June 15 6 The epicenter was determined to have been located at 39 5 Latitude 140 6 Longitude and the earthquake had an estimated magnitude of Mw8 5 7 20th century edit Major seismic activity on the Sanriku coast during the 20th century includes 1933 Sanriku earthquake More than 3 000 people died the casualties were caused by the subsequent tsunami This quake tsunami was not on the scale of the March 2011 disaster nor earlier disasters noted above 1978 Miyagi earthquake Damage was greatest around Sendai The earthquake triggered widespread landslides 8 9 1994 offshore Sanriku earthquake Damage in Hachinohe Aomori 10 21st century edit Significant seismic events which devastated Sanriku coastal communities in the 21st century include 2003 Miyagi earthquake There were two major earthquakes in 2003 in Miyagi Prefecture The first quake in May injured 171 and caused 97 3 million in damage 11 Another quake in July injured 676 More than 11 000 buildings were affected causing an estimated 195 4 million in damage 12 2005 Miyagi earthquake The seismic event was originally recorded by the United States Geological Survey as a 7 2 magnitude earthquake on the Moment magnitude scale but the Japan Meteorological Agency called it a magnitude 6 9 earthquake The slippage in the seabed subduction zone was located about 330 miles 530 kilometres east northeast of Tokyo about 24 miles 39 kilometres below the surface of the Pacific Ocean The Japan Meteorological Agency issued a tsunami warning almost immediately and warnings were also issued for the northwest coast of the United States 2011 Tōhoku earthquake and tsunami In March 2011 the largest earthquake ever recorded in Japan struck off the Sanriku coast setting off a 10 metres 33 feet tsunami The 9 0 magnitude quake near Tohoku was comparable in scale to undersea seismic events near Indonesia in 2004 3rd largest on record and near Chile in 2010 6th largest 13 It caused 15 889 deaths 6 152 injured and 2 609 people missing across twenty prefectures with an estimated 235 billion in property damage In the list of 45 most powerful earthquakes recorded worldwide since 1500 there are five that appear to be clustered in a 8 year span in 2004 2005 2010 2011 2012 with the largest being the 2004 Indian Ocean earthquake of magnitude 9 1 Prior to this no sizable earthquake occurred There was another apparent cluster in 1960 1963 1964 1965 which contained the largest recorded earthquake the 1960 Valdivia earthquake of magnitude 9 4 However experts construe this as a statistical anomaly or random chance 13 14 The phenomenon of comparably large quakes that happen on the same or neighbouring faults within months of each other for example the Miyagi quakes in 2003 can be explained by a sound geological mechanism This does not fully demonstrate a relationship between events separated by longer periods and greater distances 14 Seismic mechanisms editEarthquakes occur where the Pacific Plate meets the plate beneath northern Honshu in a subduction zone 15 The Pacific plate which moves at a rate of 8 to 9 cm 3 1 to 3 5 in per year dips under Honshu s underlying plate releasing large amounts of energy This motion pulls the upper plate down until the stress builds up enough to cause a seismic event Quakes of large magnitudes in the Sanriku region can have a rupture length of hundreds of kilometers and this generally requires a long relatively straight fault surface However the plate boundary and subduction zone in this area is not very straight 16 The epicentral region of an earthquake is defined as an elliptical area which encompasses the location of highest felt intensity of an earthquake This term is used for identifying the likely epicenter for earthquakes and tsunami in the history of the Sanriku coat The hypocentral region of Sanriku coastal earthquakes can occur in locations extending from offshore Aomori Prefecture to offshore Ibaraki Prefecture See also editSanriku earthquake Sanriku tsunami Seismicity in Japan 2011 Tohoku earthquake 1585 Aleutian Islands earthquake a distant tsunami which is said to have struck Japan Notes edit nbsp Wikinews has related news Quake measuring 6 9 off Japan s Honshu coast Evaluation of Major Subduction zone Earthquake Headquarters for Earthquake Research Promotion 2008 Archived from the original on 8 March 2022 Retrieved 17 March 2022 Saw tooth Sanriku Coastline 三陸リアス式海岸 Sanriku riasushiki kaigan at Nippon Kichi Satake Kenji 2005 Tsunamis Case Studies and Recent Developments Advances in Natural and Technological Hazards Research Book 23 Springer p 99 Bibcode 2005tcsr book S ISBN 978 1402033261 Signs of 6 massive tsunami over past 6 000 years found in disaster hit city the Mainichi Daily News Archived from the original on 2011 08 24 Retrieved 2011 09 04 Minoura Koji 30 June 2001 津波災害は繰り返す in Japanese Tohoku University Retrieved 14 March 2011 Online NOAA Japan Significant Earthquake Database U S National Oceanic and Atmospheric Administration NOAA National Geophysical Data Center NGDC Nishimura T Miura S Tachibana K Hashimoto K Sato T Hori S Murakami E Kono T Nid K Mishina M Hirasawa T amp Miyazaki S 2000 Distribution of seismic coupling on the subducting plate boundary in northeastern Japan inferred from GPS observations Tectonophysics 323 3 4 217 238 Bibcode 2000Tectp 323 217N doi 10 1016 S0040 1951 00 00108 6 USGS Significant Earthquakes of the World 1978 Archived from the original on 23 January 2010 Retrieved 6 July 2010 Sidle R C et al 1985 Hillslope stability and land use pp 1 9 p 1 at Google Books Nakayama and Takeo Slip history of the 1994 Sanriku Haruka Oki Japan earthquake deduced from strong motion data Bulletin of the Seismological Society of America Vol 87 No 4 p 918 Disaster Control Research Center Tohoku University May 26 2003 Miyagi Oki earthquake Archived September 7 2012 at archive today Disaster Control Research Center July 26 2003 Northern Miyagi earthquake Archived August 4 2012 at archive today a b Pappas Stephanie Sumatra Japan Chile Are Earthquakes Getting Worse LiveScience 11 March 2011 a b Brahic Catherine The megaquake connection Are huge earthquakes linked New Scientist UK 16 March 2011 Sample Ian Japan earthquake and tsunami what happened and why The Guardian UK 11 March 2011 retrieved 14 Mar 2011 Maugh Thomas H Size of Japan s quake surprises seismologists Los Angeles Times US 11 March 2011 retrieved 11 Mar 2011References editSidle R C Pearce A J O Loughlin C L 1985 Hillslope stability and land use Washington D C American Geophysical Union ISBN 978 0 87590 315 6External links edit Strong Earthquake Shakes Northern Japan Associated Press November 14 2005 Japan quake prompts tsunami alert CNN com November 14 2005 Technical information United States Geological Survey Earthquake shakes Japan small tsunamis measured Retrieved from https en wikipedia org w index php title Seismicity of the Sanriku coast amp oldid 1154785598, wikipedia, wiki, book, books, library,

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