This article is about earthquakes along the Nankai megathrust fault generally. For those earthquakes that affect the Nankai region specifically, see Nankai earthquakes.
The earthquakes occur with a return period of about 90–200 years, and often occur in pairs, where a rupture along one part of the fault is followed by a rupture elsewhere on the fault, notably the 1854 Ansei-Tōkai earthquake and the 1854 Ansei-Nankai earthquake the next day, and the 1944 Tōnankai earthquake, followed by the 1946 Nankaidō earthquake. In one recorded case (the 1707 Hōei earthquake) the fault ruptured along its entire length. All of these great earthquakes have resulted in damaging tsunamis, which are particularly damaging due to the Japanese population being concentrated on the Taiheiyō Belt, especially the coastal cities of Tokyo and Osaka, the two most populous in Japan. The area remains seismically active, and future earthquakes are anticipated, with a high risk of a Nankai earthquake in the near future, which could be potentially very damaging.
The Nankai Trough is the surface expression of the subduction zone between the Philippine Sea and Amur plates. Honshu itself is formed from the island arc developed over the subducting plate.[1] The megathrust boundary extends about 700 km from the southern end of Kyūshū to the triple junction with the Okhotsk Plate near Mount Fuji. At its southwestern end, there is another triple junction, where the overriding plate becomes the Okinawa Plate.[2]
Megathrust geometryedit
The megathrust dip increases from about 5° near the surface to 10° as it passes beneath the coast of Honshu. Analysis of seismic reflection data suggests that some of the displacement is carried by a splay fault dipping at about 25°.[3] This 'megasplay' fault system has caused an unusually thick section of fluid-rich sedimentary rocks to be deeply underthrust. The presence of this 'weak' zone may lead to shallow coseismic rupture along the megasplay faults during megathrust earthquakes, explaining the large tsunamis created by these events.[4]
Historical seismicityedit
Rupture areas on the Nankai trough megathrust showing names of earthquakes equating to each areaRupture areas in historical order, showing pairs
The Nankai megathrust is thought to have caused at least 12 major earthquakes in the last ca. 1300 years. The pattern of historical seismicity reveals that the megathrust surface is segmented, with five separate zones of rupturing identified, conventionally labelled A–E, from west to east.[5] Earthquakes involving the A+B segments are generally referred to as Nankai (literally South Sea) earthquakes, C+D Tonankai (literally Southeast Sea) earthquakes and C+D+E Tokai (literally East Sea) earthquakes. The earthquake repeat intervals are generally in the range 90–200 years.
On all but one occasion, rupture of segment C (±D ±E) has been followed by rupture of segments A+B within a few years. This behaviour has been reproduced by modelling the viscoelastic response of the megathrust fault plane with lateral variations in both convergence rate and frictional properties.[5]
Future earthquake riskedit
The northeasternmost part of the megathrust, segment E, has not ruptured since 1854. A future great earthquake involving rupture along this and possibly other segments has been proposed as a major risk for the southern coast of Honshu.[6] In 1999, the likelihood of the occurrence of a great earthquake in the Tokai area in the 2000-2010 period was estimated to be in the range of 0.35–0.45.[7] Despite the uncertainty of when such an earthquake will occur, local authorities are already taking action to prepare residents for what they regard as an inevitability.[8]
Potential effectsedit
The Japanese government estimates that a major earthquake on the Nankai Trough would cause 169.5 trillion yen in direct damage and 50.8 trillion yen in economic losses for the following year. A study by the Japan Society of Civil Engineers in 2018 estimated that the long-term damage from the earthquake could result in 1,240 trillion yen in economic losses over a 20-year period.[9] It is predicted that the economic damage is likely to be 10 times higher than for the 2011 Tōhoku earthquake and tsunami.[10] A death toll as high as 230,000 has been suggested for such an event.[11]
List of occurrencesedit
All the dates shown in the table use the Gregorian calendar. Some sources use the Julian calendar for the earlier earthquakes in the list.
^Taira, A. (2001). "Tectonic evolution of the Japanese island arc system" (PDF). Annu. Rev. Earth Planet. Sci. 29: 109–134. Bibcode:2001AREPS..29..109T. doi:10.1146/annurev.earth.29.1.109. Retrieved 2009-12-06.
^Neall, V.E.; Trewick S.A. (2008). "The age and origin of the Pacific islands: a geological overview". Philos Trans R Soc Lond B Biol Sci. 363 (1508): 3293–3308. doi:10.1098/rstb.2008.0119. PMC2607379. PMID 18768382.
^Cummins, P.R.; Hori T.; Kaneda Y. (2001). "Splay fault and megathrust earthquake slip in the Nankai Trough" (PDF). Earth Planets Space. 53 (4): 243–248. Bibcode:2001EP&S...53..243C. doi:10.1186/BF03352381. S2CID 56221703. Retrieved 2009-12-01.
^Bangs, N.L.B.; Moore G.G.; Gulick S.P.S.; Pangborn E.M.; Tobin H.J.; Kuramoto S.; Taira A. (2009). (PDF). Earth and Planetary Science Letters. 284 (1–2): 44–49. Bibcode:2009E&PSL.284...44B. doi:10.1016/j.epsl.2009.04.026. Archived from the original (PDF) on 2009-09-19. Retrieved 2009-12-01.
^ abHirahara, K.; Kato N.; Miyatake T.; Hori T.; Hyodo M.; Inn J.; Mitsui N.; Sasaki T.; Miyamura T.; Nakama Y.; Kanai T. (2004). "Simulation of Earthquake Generation Process in a Complex System of Faults" (PDF). Annual Report of the Earth Simulator Center April 2004 - March 2005. pp. 121–126. Retrieved 2009-11-14.
^Ando, M. (1975). "Source mechanisms and tectonic significance of historical earthquakes along the Nankai Trough, Japan". Tectonophysics. 27 (2): 119–140. Bibcode:1975Tectp..27..119A. doi:10.1016/0040-1951(75)90102-X.
^Rikitake, T (1999). "Probability of a great earthquake to recur in the Tokai district, Japan" (PDF). Earth Planets Space. 51 (3): 147–157. Bibcode:1999EP&S...51..147R. doi:10.1186/BF03352219. S2CID 41377767. Retrieved 2009-12-05.
^Yamanashi Prefectural Disaster Prevention Safety Center. "A Disaster Prevention and Earthquake Experience Guide" (PDF). Retrieved 5 December 2009.
^Sasaki, Eisuke (8 June 2018). "Study: Damage from Nankai quake could hit 1,240 trillion yen". The Asahi Shimbun. Retrieved 17 June 2018.
^Kamata, Hiroki (20 February 2021). "｢被害は東日本大震災の10倍超｣2030～40年に想定される西日本大震災という時限爆弾". PRESIDENT Online (in Japanese). Retrieved 22 February 2021.
^. Nippon.com. 7 June 2019. Archived from the original on 20 Feb 2023. Retrieved 2 August 2019.
^ abcdefghijklmIISEE. "Catalog of Damaging Earthquakes in the World (Through 2007)". Retrieved 2009-11-13.
^ abcdefghijklmYonekura, N. (1975). "Quaternary tectonic movements in the outer arc on southwest Japan with special reference to seismic crustal deformation". Bulletin Department of Geography University of Tokyo. 7: 19–71.
January 01, 1970
nankai, megathrust, earthquakes, this, article, about, earthquakes, along, nankai, megathrust, fault, generally, those, earthquakes, that, affect, nankai, region, specifically, nankai, earthquakes, japanese, 南海トラフ巨大地震, hepburn, nankai, torafu, kyodai, jishin, . This article is about earthquakes along the Nankai megathrust fault generally For those earthquakes that affect the Nankai region specifically see Nankai earthquakes Nankai megathrust earthquakes Japanese 南海トラフ巨大地震 Hepburn Nankai Torafu Kyodai Jishin are great megathrust earthquakes that occur along the Nankai megathrust the fault under the Nankai Trough which forms the plate interface between the subducting Philippine Sea Plate and the overriding Amurian Plate part of the Eurasian Plate which dips beneath southwestern Honshu Japan The fault is divided into five segments in three zones which rupture separately or in combination and depending on location the resulting earthquakes are subdivided by zone from west to east into Nankai earthquakes Tōnankai earthquakes and Tōkai earthquakes Envisioned focal area of M9 1 Nankai Trough Megathrust Earthquake by Headquarters for Earthquake Research Promotion 2013 The earthquakes occur with a return period of about 90 200 years and often occur in pairs where a rupture along one part of the fault is followed by a rupture elsewhere on the fault notably the 1854 Ansei Tōkai earthquake and the 1854 Ansei Nankai earthquake the next day and the 1944 Tōnankai earthquake followed by the 1946 Nankaidō earthquake In one recorded case the 1707 Hōei earthquake the fault ruptured along its entire length All of these great earthquakes have resulted in damaging tsunamis which are particularly damaging due to the Japanese population being concentrated on the Taiheiyō Belt especially the coastal cities of Tokyo and Osaka the two most populous in Japan The area remains seismically active and future earthquakes are anticipated with a high risk of a Nankai earthquake in the near future which could be potentially very damaging Contents 1 Tectonic setting 2 Megathrust geometry 3 Historical seismicity 4 Future earthquake risk 4 1 Potential effects 5 List of occurrences 6 See also 7 ReferencesTectonic setting editThe Nankai Trough is the surface expression of the subduction zone between the Philippine Sea and Amur plates Honshu itself is formed from the island arc developed over the subducting plate 1 The megathrust boundary extends about 700 km from the southern end of Kyushu to the triple junction with the Okhotsk Plate near Mount Fuji At its southwestern end there is another triple junction where the overriding plate becomes the Okinawa Plate 2 Megathrust geometry editThe megathrust dip increases from about 5 near the surface to 10 as it passes beneath the coast of Honshu Analysis of seismic reflection data suggests that some of the displacement is carried by a splay fault dipping at about 25 3 This megasplay fault system has caused an unusually thick section of fluid rich sedimentary rocks to be deeply underthrust The presence of this weak zone may lead to shallow coseismic rupture along the megasplay faults during megathrust earthquakes explaining the large tsunamis created by these events 4 Historical seismicity edit nbsp Rupture areas on the Nankai trough megathrust showing names of earthquakes equating to each area nbsp Rupture areas in historical order showing pairs The Nankai megathrust is thought to have caused at least 12 major earthquakes in the last ca 1300 years The pattern of historical seismicity reveals that the megathrust surface is segmented with five separate zones of rupturing identified conventionally labelled A E from west to east 5 Earthquakes involving the A B segments are generally referred to as Nankai literally South Sea earthquakes C D Tonankai literally Southeast Sea earthquakes and C D E Tokai literally East Sea earthquakes The earthquake repeat intervals are generally in the range 90 200 years On all but one occasion rupture of segment C D E has been followed by rupture of segments A B within a few years This behaviour has been reproduced by modelling the viscoelastic response of the megathrust fault plane with lateral variations in both convergence rate and frictional properties 5 Future earthquake risk editThe northeasternmost part of the megathrust segment E has not ruptured since 1854 A future great earthquake involving rupture along this and possibly other segments has been proposed as a major risk for the southern coast of Honshu 6 In 1999 the likelihood of the occurrence of a great earthquake in the Tokai area in the 2000 2010 period was estimated to be in the range of 0 35 0 45 7 Despite the uncertainty of when such an earthquake will occur local authorities are already taking action to prepare residents for what they regard as an inevitability 8 Potential effects edit The Japanese government estimates that a major earthquake on the Nankai Trough would cause 169 5 trillion yen in direct damage and 50 8 trillion yen in economic losses for the following year A study by the Japan Society of Civil Engineers in 2018 estimated that the long term damage from the earthquake could result in 1 240 trillion yen in economic losses over a 20 year period 9 It is predicted that the economic damage is likely to be 10 times higher than for the 2011 Tōhoku earthquake and tsunami 10 A death toll as high as 230 000 has been suggested for such an event 11 List of occurrences editAll the dates shown in the table use the Gregorian calendar Some sources use the Julian calendar for the earlier earthquakes in the list Date Time Name Magnitude Ruptured segments Tsunami max wave height m Coordinates Fatalities Sources 1 684 11 29 22 00 684 Hakuho earthquake 8 4 A B C D E 3 0 32 48 N 134 18 E 32 8 N 134 3 E 32 8 134 3 many 12 13 14 2 887 8 26 16 00 Ninna Nankai earthquake 8 6 A B C D E 10 0 33 00 N 135 00 E 33 0 N 135 0 E 33 0 135 0 many 12 13 14 3 1096 12 17 08 00 8 4 C D E 7 0 34 00 N 137 30 E 34 0 N 137 5 E 34 0 137 5 12 13 14 4 1099 2 22 06 00 Kōwa Nankaido earthquake 8 0 A B 33 00 N 135 30 E 33 0 N 135 5 E 33 0 135 5 13 14 5 1360 11 22 Uncertain event 7 0 6 0 33 24 N 136 12 E 33 4 N 136 2 E 33 4 136 2 12 13 14 6 1361 8 03 04 00 1361 Shōhei earthquake 8 4 A B C D 33 00 N 135 00 E 33 0 N 135 0 E 33 0 135 0 13 14 7 1498 9 20 08 00 1498 Meiō Nankaidō earthquake 8 6 A B C D E 34 00 N 138 00 E 34 0 N 138 0 E 34 0 138 0 thousands 13 14 8 1605 2 3 20 00 1605 Keichō Nankaido earthquake 7 9 A B C D 10 0 33 00 N 135 00 E 33 0 N 135 0 E 33 0 135 0 thousands 12 13 14 9 1707 10 28 14 00 1707 Hōei earthquake 8 6 A B C D E 25 7 33 00 N 136 00 E 33 0 N 136 0 E 33 0 136 0 5 000 12 13 14 10 1854 12 23 09 00 1854 Tōkai earthquake 8 4 C D E 21 0 34 00 N 137 48 E 34 0 N 137 8 E 34 0 137 8 2 000 12 13 14 11 1854 12 24 16 00 1854 Nankai earthquake 8 4 A B 28 0 33 00 N 135 00 E 33 0 N 135 0 E 33 0 135 0 thousands 12 13 14 12 1944 12 7 13 35 1944 Tōnankai earthquake 8 1 C D 10 0 33 34 N 136 11 E 33 57 N 136 18 E 33 57 136 18 1 251 12 13 14 13 1946 12 21 04 19 1946 Nankaidō earthquake 8 1 A B 6 6 32 56 N 135 51 E 32 93 N 135 85 E 32 93 135 85 1 330 12 13 14 See also editTokai earthquakes List of earthquakes in JapanReferences edit Taira A 2001 Tectonic evolution of the Japanese island arc system PDF Annu Rev Earth Planet Sci 29 109 134 Bibcode 2001AREPS 29 109T doi 10 1146 annurev earth 29 1 109 Retrieved 2009 12 06 Neall V E Trewick S A 2008 The age and origin of the Pacific islands a geological overview Philos Trans R Soc Lond B Biol Sci 363 1508 3293 3308 doi 10 1098 rstb 2008 0119 PMC 2607379 PMID 18768382 Cummins P R Hori T Kaneda Y 2001 Splay fault and megathrust earthquake slip in the Nankai Trough PDF Earth Planets Space 53 4 243 248 Bibcode 2001EP amp S 53 243C doi 10 1186 BF03352381 S2CID 56221703 Retrieved 2009 12 01 Bangs N L B Moore G G Gulick S P S Pangborn E M Tobin H J Kuramoto S Taira A 2009 Broad weak regions of the Nankai Megathrust and implications for shallow coseismic slip PDF Earth and Planetary Science Letters 284 1 2 44 49 Bibcode 2009E amp PSL 284 44B doi 10 1016 j epsl 2009 04 026 Archived from the original PDF on 2009 09 19 Retrieved 2009 12 01 a b Hirahara K Kato N Miyatake T Hori T Hyodo M Inn J Mitsui N Sasaki T Miyamura T Nakama Y Kanai T 2004 Simulation of Earthquake Generation Process in a Complex System of Faults PDF Annual Report of the Earth Simulator Center April 2004 March 2005 pp 121 126 Retrieved 2009 11 14 Ando M 1975 Source mechanisms and tectonic significance of historical earthquakes along the Nankai Trough Japan Tectonophysics 27 2 119 140 Bibcode 1975Tectp 27 119A doi 10 1016 0040 1951 75 90102 X Rikitake T 1999 Probability of a great earthquake to recur in the Tokai district Japan PDF Earth Planets Space 51 3 147 157 Bibcode 1999EP amp S 51 147R doi 10 1186 BF03352219 S2CID 41377767 Retrieved 2009 12 05 Yamanashi Prefectural Disaster Prevention Safety Center A Disaster Prevention and Earthquake Experience Guide PDF Retrieved 5 December 2009 Sasaki Eisuke 8 June 2018 Study Damage from Nankai quake could hit 1 240 trillion yen The Asahi Shimbun Retrieved 17 June 2018 Kamata Hiroki 20 February 2021 被害は東日本大震災の10倍超 2030 40年に想定される西日本大震災という時限爆弾 PRESIDENT Online in Japanese Retrieved 22 February 2021 A Disaster to Dwarf 3 11 The Predicted Nankai Quake Nippon com 7 June 2019 Archived from the original on 20 Feb 2023 Retrieved 2 August 2019 a b c d e f g h i j National Geophysics Data Center NGDC Tsunami Event Database Retrieved 2009 11 13 a b c d e f g h i j k l m IISEE Catalog of Damaging Earthquakes in the World Through 2007 Retrieved 2009 11 13 a b c d e f g h i j k l m Yonekura N 1975 Quaternary tectonic movements in the outer arc on southwest Japan with special reference to seismic crustal deformation Bulletin Department of Geography University of Tokyo 7 19 71 Retrieved from https en wikipedia org w index php title Nankai megathrust earthquakes amp oldid 1225213786, wikipedia, wiki, book, books, library,
