Wikipedia

2026 Sanriku earthquake

On 20 April 2026 at 16:53 JST (07:53 UTC), a MJMA 7.7 (Mw 7.4–7.5) earthquake struck off the Sanriku Coast of Honshu, Japan, along the Japan Trench. The earthquake caused strong shaking in Iwate and Aomori, with a maximum intensity of 5-upper (5+) on the Japan Meteorological Agency seismic intensity scale, recorded in Hashikami, Aomori. Additionally, it generated long-period ground motion of class 3 in southern Akita and northern Miyagi prefectures.[1]

2026 Sanriku earthquake
USGS ShakeMap
2026 Sanriku earthquake is located in Japan
2026 Sanriku earthquake
Morioka
Morioka
Hachinohe
Hachinohe
Sendai
Sendai
UTC time2026-04-20 07:53:00
ISC event645637641
USGS-ANSSComCat
Local dateApril 20, 2026 (2026-04-20)
Local time16:53:00 JST (UTC+9)
Duration12 seconds
MagnitudeMJMA 7.7
Mw 7.4–7.5
Depth35 km (22 mi) (USGS)
Epicenter39°57′11″N 143°02′46″E / 39.953°N 143.046°E / 39.953; 143.046
FaultJapan Trench
TypeThrust
Areas affectedTōhoku region and Hokkaido, Japan
Total damage233 structures damaged
Max. intensityJMA 5+ (MMI VI)
Peak acceleration0.404 g
Peak velocity15.01 cm/s (5.91 in/s)
Tsunami79 cm (31 in) (Kuji, Iwate)
Foreshocks162 ≥Mw 4.0
Mw 6.8 on November 9, 2025 (Strongest)
Aftershocks17 ≥Mw 4.0
Mw 5.6 on April 20, 2026 (Strongest)
Casualties10 injuries

Tectonic setting

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The northern parts of Honshu and the island of Hokkaido lie above the convergent plate boundary where the Pacific plate is subducting beneath the Okhotsk microplate. The convergence rate across this boundary lies in the range of 7.9–9.2 cm per year.[2] The plate interface in the area of the earthquake epicenter shows an abrupt increase in dip from about 5° to about 15°, 80 km landward of the Japan Trench.[3] This part of the plate boundary has been the location of many powerful historical earthquakes, dating back to the 869 Sanriku earthquake and the devastating 2011 Tōhoku earthquake. Most of these events relate to rupture along the plate interface, but some, such as the 1933 Sanriku earthquake,[4] involved deformation within the subducting plate. According to the studies of past great earthquakes, a weak seismic coupling is suggested in the offshore Sanriku region.[5] From the distribution of past seismicity, the width of coupling at 40°N was assumed to be about 150 km.[6]

Earthquake

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The United States Geological Survey (USGS) said it measured the earthquake at Mw 7.4 and was caused by a east-northeast-dipping, southwest–northeast-striking thrust fault at a depth of 35 km (22 mi),[7] while the Japan Meteorological Agency (JMA) put the preliminary magnitude at MJMA 7.5[8] and later updated to MJMA 7.7.[9] Tremors were felt from Hokkaido to Aichi.[9] The Global Centroid Moment Tensor (GCMT) assigned the earthquake a moment magnitude of Mw 7.5.[10] A USGS finite fault model estimates a rupture area of 70 km × 65 km (43 mi × 40 mi), with a maximum slip of 4.735 m (15.53 ft) near the hypocenter. The observed source time function gives a 12-second duration for the earthquake, with the greatest phase of seismic moment release occurring less than 10 seconds after initiation. A USGS seismic installation at Shingō, Aomori recorded 15.01 cm/s (5.91 in/s) in ground velocity (pgv), while another installation at Morioka, Iwate recorded a peak ground acceleration (pga) of 0.404 g.[7]

A foreshock sequence preceding the mainshock began in November 2025; 162 foreshocks exceeding Mw 4.0 occurred, including five Mw 6.0+ events,[11] the strongest of which measured Mw 6.8.[12] By 23 April, 17 aftershocks measuring Mw 4.0 or higher occurred,[11] the strongest measuring Mw 5.6.[13]

Locations with a seismic intensity of Shindo 4 and higher[9]
Intensity Prefecture Locations
5+ Aomori Hashikami
5− Hachinohe, Shichinohe, Tohoku, Oirase, Gonohe, Nanbu
Iwate Miyako, Morioka, Fudai, Ninohe, Hachimantai, Yahaba, Hanamaki
Miyagi Tome, Wakuya
4 Aomori Towada, Misawa, Noheji, Rokunohe, Yokohama, Rokkasho, Sannohe, Takko, Shingō, Aomori, Tsugaru, Hiranai, Sotogahama, Fujisaki, Mutsu, Higashidōri
Iwate Kuji, Yamada, Iwaizumi, Tanohata, Noda, Hirono, Takizawa, Shizukuishi, Kuzumaki, Iwate, Shiwa, Karumai, Kunohe, Ichinohe, Kitakami, Tōno, Ichinoseki, Ōshū, Nishiwaga, Kanegasaki, Hiraizumi, Ōfunato, Kamaishi, Sumita, Ōtsuchi
Miyagi Kesennuma, Kurihara, Ōsaki, Shikama, Misato, Natori, Kakuda, Iwanuma, Zaō, Ōgawara, Kawasaki, Marumori, Watari, Yamamoto, Sendai, Ishinomaki, Higashimatsushima, Matsushima
Hokkaido Hakodate, Niikappu
Akita Mitane, Ikawa, Akita, Yurihonjō, Nikaho, Ōdate, Kazuno, Kitaakita, Yokote, Daisen, Misato
Yamagata Sakata, Mikawa, Murayama, Nakayama
Fukushima Kunimi

Tsunami

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The JMA issued a tsunami warning for waves reaching up to 3 metres (9.8 ft) high in parts of Iwate Prefecture, Aomori, and Hokkaido Prefectures. These warnings were later downgraded to advisories,[14] before being lifted at 23:50 JST.[15] An 80-centimeter-high (31 in) tsunami struck Kuji, Iwate.[16] At Miyako[17] and Urakawa, Hokkaido, the tsunami was 40 centimeters (16 in) high,[17] while 30-centimeter (12 in) waves were observed in Hiroo and Erimo in Hokkaido and Sendai, Miyagi.[18][15]

Impact

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Ten people were injured, two in Hokkaido, and four each in Aomori and Iwate prefectures. Two of the victims were seriously injured.[19] At least 232 buildings were damaged in Aomori Prefecture.[20] A road was damaged in Ishinomaki, Miyagi Prefecture.[21] Roughly 200 households lost power in Hiraizumi, Iwate.[16] Evacuation orders were issued to 82,811 households and 175,957 people from a total of 13 cities, 21 towns and 6 villages in Hokkaido, Aomori, Iwate, Miyagi, and Fukushima Prefectures.[16] Schools were closed for April 21 in Urakawa,[15] and several schools in Aomori Prefecture.[22] The earthquake resulted in suspension of Shinkansen lines including the Hokkaido, Tokaido and Tōhoku Shinkansen.[15][16] Ferry services between Aomori and Hakodate were also cancelled.[15]

Response

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The JMA issued an Off the coast of Hokkaido and Sanriku subsequent earthquake advisory until April 27, warning about a possibility of a stronger earthquake.[23] Along with the Cabinet Office, the Japan Meteorological Agency stated that the chance of a "megaquake" exceeding magnitude eight would be increased tenfold over during this period, up to 1% following the quake from a background risk of 0.1%.[24]

Misinformation

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Following the earthquake, social media posts circulating on X uploaded by various accounts in and outside Japan claimed to show footage of the earthquake using videos and images of the 2024 Noto earthquake and the 2011 Tōhoku earthquake and tsunami as well as AI-generated content. As a result, the Ministry of Internal Affairs and Communications requested X and other major social media sites "to take appropriate measures based on the terms of use".[25][26]

See also

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References

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  1. ↑ "Evaluation of Earthquake Offshore of Sanriku on April 20, 2026". Headquarters for Earthquake Research Promotion. 14 May 2026. Retrieved 4 June 2026.{{cite news}}: CS1 maint: url-status (link)
  2. ↑ Nishimura, T.; Miura S.; Tachibana K.; Hashimoto K.; Sato T.; Hori S.; Murakami E.; Kono T.; Nida 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.
  3. ↑ Ito, A.; Fujie G.; Tsuru T.; Kodaira S.; Nakanishi A. & Kaneda Y. (2004). "Fault plane geometry in the source region of the 1994 Sanriku-oki earthquake". Earth and Planetary Science Letters. 223 (1–2): 163–175. Bibcode:2004E&PSL.223..163I. doi:10.1016/j.epsl.2004.04.007.
  4. ↑ Kanamori, H. (1971). "Seismological evidence for a lithospheric normal faulting – the Sanriku earthquake of 1933" (PDF). Physics of the Earth and Planetary Interiors. 4 (4): 289–300. Bibcode:1971PEPI....4..289K. doi:10.1016/0031-9201(71)90013-6. Archived from the original (PDF) on 19 March 2012. Retrieved 13 July 2011.
  5. ↑ Takahashi, N.; Kodaira S.; Tsuru T.; Park J-O.; Kaneda Y.; Suyehiro K.; Kinoshita H.; Abe S.; Nishino M. & Hino R. (2004). "Seismic structure and seismogenesis off Sanriku region, northeastern Japan". Geophysical Journal International. 159 (1): 129–145. Bibcode:2004GeoJI.159..129T. doi:10.1111/j.1365-246X.2004.02350.x.
  6. ↑ Kawasaki, I.; Asai Y. & Tamura Y. (2001). "Space–time distribution of interplate moment release including slow earthquakes and the seismo-geodetic coupling in the Sanriku-oki region along the Japan trench" (PDF). Tectonophysics. 330 (3–4): 276–283. Bibcode:2001Tectp.330..267K. doi:10.1016/S0040-1951(00)00245-6. Archived (PDF) from the original on 4 October 2011. Retrieved 13 July 2011.
  7. 1 2 ANSS. "M 7.4 - 100 km ENE of Miyako, Japan 2026". Comprehensive Catalog. U.S. Geological Survey.
  8. ↑ "Japan says bigger tsunami may hit after earthquake off north-east coast - follow live". BBC News. 20 April 2026. Retrieved 20 April 2026.
  9. 1 2 3 "Earthquake Information". Japan Meteorological Agency. 20 April 2026. Archived from the original on 25 April 2026. Retrieved 20 April 2026.
  10. ↑ "Global CMT Catalog Search". Global Centroid Moment Tensor. 20 April 2026. Retrieved 6 February 2023.
  11. 1 2 "USGS earthquake catalog". United States Geological Survey.
  12. ↑ ANSS. "M 6.8 - 122 km E of Yamada, Japan 2025". Comprehensive Catalog. U.S. Geological Survey.
  13. ↑ ANSS. "M 5.6 - 113 km E of Miyako, Japan 2026". Comprehensive Catalog. U.S. Geological Survey.
  14. ↑ "Japan earthquake mapped: Country on high alert for large quake after tsunami warnings". The Independent. Archived from the original on 20 April 2026. Retrieved 20 April 2026.
  15. 1 2 3 4 5 【速報中】北海道太平洋沿岸中部の津波警報は注意報に切り替え 後発地震注意情報発表 道内約4万4千人に避難指示 [[Breaking News] Tsunami warning in the central Pacific coast of Hokkaido is switched to a warning. Information on warning about late earthquakes is announced. About 44,000 people in the Hokkaido are ordered to evacuate.]. Hokkaido Shimbun (in Japanese). 20 April 2026. Archived from the original on 20 April 2026. Retrieved 20 April 2026.
  16. 1 2 3 4 【速報中】岩手・久慈で８０ｃｍの津波、「後発地震注意情報」発表…津波警報は津波注意報に切り替え [[Breaking news] 80 cm tsunami in Iwate and Kuji, "recent earthquake warning information" announced ... Tsunami warning switched to tsunami warning]. Yomiuri Shimbun (in Japanese). 20 April 2026. Retrieved 20 April 2026.
  17. 1 2 三陸沖M7.7地震、岩手県久慈港に津波80センチ 後発地震情報も発表 [M7.7 earthquake off the Sanriku coast, 80 cm tsunami in Kuji Port, Iwate Prefecture, late earthquake information was also announced]. Iwate Nippo (in Japanese). 20 April 2026. Archived from the original on 20 April 2026. Retrieved 20 April 2026.
  18. ↑ 三陸沖地震で最大８０ｃｍの津波、昨年１２月以来の「後発地震注意情報」…１週間はすぐ逃げられる態勢維持を [A tsunami of up to 80 cm in the Sanriku earthquake, the "recomnt earthquake warning information" since December last year ... Maintain a posture that can escape immediately for a week]. Yomiuri Shimbun (in Japanese). 20 April 2026. Archived from the original on 20 April 2026. Retrieved 20 April 2026.
  19. ↑ 三陸沖を震源とする地震による被害及び 消防機関等の対応状況（第１１報） [Damage caused by the earthquake off the coast of Sanriku and the response of fire departments and other organizations (Report No. 11)] (PDF). Fire and Disaster Management Agency. 21 April 2026. Archived (PDF) from the original on 25 April 2026. Retrieved 24 April 2026.
  20. ↑ 令和8年4月20日青森県三陸沖地震に係る被害報 (第8報) (Report) (in Japanese). Aomori Prefectural Government. 27 April 2026.
  21. ↑ 地震被害「重傷2人軽傷4人」官房長官 宮城では道路陥没も [Earthquake damage "2 seriously injured 4 minor injured" Chief Cabinet Secretary Road collapse in Miyagi] (Report) (in Japanese). NHK. 20 April 2026. Archived from the original on 21 April 2026. Retrieved 21 April 2026.
  22. ↑ 「後発地震注意情報」今後1週間は大規模地震に備え警戒 青森で震度5強 踏切内で道路陥没、ビルの外壁落下も｜FNNプライムオンライン [“earthquake warning information" Prepare for a large-scale earthquake in the next week, be alert, earthquake intensity 5 in Aomori, road collapses at the level crossing, building exterior walls fall]. Fuji News Network (in Japanese). 21 April 2026. Archived from the original on 22 April 2026. Retrieved 21 April 2026.
  23. ↑ 通算2度目の後発地震注意情報 対象自治体は? 青森震度5強 [Warning information for the second late earthquake in a rid. Which local government is the target? Aomori earthquake intensity 5+]. Mainichi Shimbun (in Japanese). 20 April 2026. Archived from the original on 21 April 2026. Retrieved 20 April 2026.
  24. ↑ Yamaguchi, Mari (20 April 2026). "Japan warns of slightly increased risk of mega-quake after a 7.7-magnitude one". AP News. Archived from the original on 20 April 2026. Retrieved 20 April 2026.
  25. ↑ Sanada, Mine; Sometaya, Ryūta (21 April 2026). 「地震が襲った瞬間」実は能登半島地震の動画 またSNSでフェイク ["The moment the earthquake struck" is actually a video of the Noto Peninsula earthquake and a fake on SNS again]. The Asahi Shimbun (in Japanese). Archived from the original on 21 April 2026. Retrieved 21 April 2026.
  26. ↑ 津波警報直後から SNSで偽情報・偽動画相次ぐ 注意を [Immediately after the tsunami warning, please be aware of the series of false information and fake videos on SNS]. NHK (in Japanese). 20 April 2026. Archived from the original on 21 April 2026. Retrieved 21 April 2026.
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