2026 Sanriku earthquake
Earthquake off the coast of Iwate Prefecture, Japan
From Wikipedia, the free encyclopedia
On 20 April 2026, at 16:53 JST (07:53 UTC), a MJMA 7.5 (Mw 7.4–7.5) earthquake struck off the Sanriku Coast of Honshu, Japan, along the Japan Trench.[1]
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USGS ShakeMap | |
  | |
| UTC time | 2026-04-20 07:53:00 |
|---|---|
| ISC event | 645637641 |
| USGS-ANSS | ComCat |
| Local date | April 20, 2026 |
| Local time | 16:53:00 JST (UTC+9) |
| Duration | 12 seconds |
| Magnitude | MJMA 7.5 Mw 7.4–7.5 |
| Depth | 35 km (22 mi) (USGS) |
| Epicenter | 39.953°N 143.046°E |
| Fault | Japan Trench |
| Type | Thrust |
| Areas affected | Tōhoku region and Hokkaido, Japan |
| Total damage | 40 structures damaged |
| Max. intensity | JMA 5+ (MMI VI) |
| Peak acceleration | 0.404 g |
| Peak velocity | 15.01 cm/s (5.91 in/s) |
| Tsunami | 80 cm (31 in) |
| Foreshocks | 162 ≥Mw 4.0 Mw 6.8 on November 9, 2025 (Strongest) |
| Aftershocks | 17 ≥Mw 4.0 Mw 5.6 on April 20, 2026 (Strongest) |
| Casualties | 10 injuries |
Tectonic setting
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]
In December 2025, a Mw 7.6 earthquake struck about 140 km (87 mi) north-northwest of the April 2026 event.
Earthquake
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 7.7[8] and later downgraded to MJMA 7.5.[9] Tremors were felt from Hokkaido to Nagoya.[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]
Tsunami
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
Ten people were injured, two in Hokkaido, and four each in Aomori and Iwate prefectures.[19] Two of the victims were seriously injured. At least 39 buildings were damaged in Aomori Prefecture. A road was damaged in Ishinomaki, Miyagi Prefecture.[20] 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.[21] 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
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.[22] 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%.[23]
Misinformation
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".[24][25]
