Japan Magnitude 7.7 Earthquake; Tsunami Advisories from Hokkaido to Fukushima Lifted
The Japan Meteorological Agency announced that all tsunami advisories issued for coastal areas from Hokkaido to Fukushima, following a magnitude 7.7 earthquake off the Sanriku coast, have been lifted. The agency also provided details on the earthquake's characteristics and historical seismic activity in the region.
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- 📰 Published: April 21, 2026 at 00:28
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Central News Agency
(Central News Agency, Tokyo, April 20 - Staff Reporter) The Japan Meteorological Agency announced this evening that the tsunami advisories issued for coastal areas from Hokkaido to Fukushima, following an earthquake of intensity 5-strong observed in Aomori Prefecture this afternoon, have been completely lifted.
The agency explained that the earthquake occurred at 4:53 PM JST (3:53 PM Taiwan time) with its epicenter located off the Sanriku coast. The earthquake's magnitude was revised upwards from the initial preliminary report of 7.5 to 7.7, and its focal depth was revised from 10 km to 19 km.
According to The Sankei Shimbun, the agency stated that generally, a 0.2 increase in earthquake magnitude represents about a doubling of released energy. Although the earthquake initially triggered tsunami advisories, it has now been confirmed that there is no further risk, leading to the complete lifting of advisories for coastal areas in Hokkaido, Aomori Prefecture, Iwate Prefecture, Miyagi Prefecture, and Fukushima Prefecture.
The Japan Meteorological Agency categorizes tsunami warnings into three levels: 'Tsunami Advisory' for tsunami heights below 1 meter; 'Tsunami Warning' for tsunami heights between 1 and 3 meters; and 'Major Tsunami Warning' for tsunami heights above 3 meters.
This earthquake occurred off the Sanriku coast, an area where the Pacific plate subducts beneath the continental plate. The agency indicated that this earthquake is believed to have been caused by the mutual compression of plates, classified as a 'reverse fault type' earthquake with vertical displacement.
This sea area has experienced frequent seismic activity in the past. In November last year, an earthquake of magnitude 6.9 occurred slightly south of the current epicenter, and a tsunami was observed. According to long-term assessments by the Japanese government's Headquarters for Earthquake Research Promotion, there is a potential risk of mega-thrust earthquakes in this region.
Historical records show that the Sanriku offshore area has experienced multiple strong earthquakes, including the 1896 Meiji Sanriku earthquake (magnitude 8.2) and the 1994 Sanriku Far Offshore earthquake (magnitude 7.6). Additionally, in 2015, following a magnitude 6.9 earthquake, successive aftershocks of magnitude 6.5 and 6.4 occurred.
Kenji Satake, Professor Emeritus at the University of Tokyo, stated that the Sanriku offshore area is inherently prone to earthquakes of magnitude 7 or higher, and this earthquake may have had a mutual influence with last year's earthquake. Continued close observation is necessary. (Editor: Chen Cheng-chien) 1150420
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(Central News Agency, Tokyo, April 20 - Staff Reporter) The Japan Meteorological Agency announced this evening that the tsunami advisories issued for coastal areas from Hokkaido to Fukushima, following an earthquake of intensity 5-strong observed in Aomori Prefecture this afternoon, have been completely lifted.
The agency explained that the earthquake occurred at 4:53 PM JST (3:53 PM Taiwan time) with its epicenter located off the Sanriku coast. The earthquake's magnitude was revised upwards from the initial preliminary report of 7.5 to 7.7, and its focal depth was revised from 10 km to 19 km.
According to The Sankei Shimbun, the agency stated that generally, a 0.2 increase in earthquake magnitude represents about a doubling of released energy. Although the earthquake initially triggered tsunami advisories, it has now been confirmed that there is no further risk, leading to the complete lifting of advisories for coastal areas in Hokkaido, Aomori Prefecture, Iwate Prefecture, Miyagi Prefecture, and Fukushima Prefecture.
The Japan Meteorological Agency categorizes tsunami warnings into three levels: 'Tsunami Advisory' for tsunami heights below 1 meter; 'Tsunami Warning' for tsunami heights between 1 and 3 meters; and 'Major Tsunami Warning' for tsunami heights above 3 meters.
This earthquake occurred off the Sanriku coast, an area where the Pacific plate subducts beneath the continental plate. The agency indicated that this earthquake is believed to have been caused by the mutual compression of plates, classified as a 'reverse fault type' earthquake with vertical displacement.
This sea area has experienced frequent seismic activity in the past. In November last year, an earthquake of magnitude 6.9 occurred slightly south of the current epicenter, and a tsunami was observed. According to long-term assessments by the Japanese government's Headquarters for Earthquake Research Promotion, there is a potential risk of mega-thrust earthquakes in this region.
Historical records show that the Sanriku offshore area has experienced multiple strong earthquakes, including the 1896 Meiji Sanriku earthquake (magnitude 8.2) and the 1994 Sanriku Far Offshore earthquake (magnitude 7.6). Additionally, in 2015, following a magnitude 6.9 earthquake, successive aftershocks of magnitude 6.5 and 6.4 occurred.
Kenji Satake, Professor Emeritus at the University of Tokyo, stated that the Sanriku offshore area is inherently prone to earthquakes of magnitude 7 or higher, and this earthquake may have had a mutual influence with last year's earthquake. Continued close observation is necessary. (Editor: Chen Cheng-chien) 1150420
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The text, images, and videos on this website may not be reproduced, publicly broadcast, publicly transmitted, or used without authorization.
Keywords: