Japan Earthquake Tsunami April 20 2026: Iwate, Aomori, Hokkaido, Miyagi Affected Areas Full List

After a magnitude 7.4 earthquake struck off the Sanriku coast at 13:23 JST on Monday, April 20, tsunami waves have reached or are actively approaching the coastlines of Iwate, Aomori, Hokkaido, Miyagi and Fukushima Prefectures. NHK has reported that the tsunami may have already hit Iwate’s coast, with the Japan Meteorological Agency confirming full tsunami warnings for three coastal zones and advisory-level alerts for five more.

Here is a complete breakdown of every area under warning, the wave heights expected, and when they are arriving.

Iwate Prefecture — Tsunami Warning, 3 Metres, Waves May Have Already Arrived

Iwate Prefecture faces the most immediate and serious threat. NHK reported that waves may have already reached the coastline, with estimated arrival times at key observation points having passed — Miyako and Kamaishi at 13:40 JST, Ofunato and Kuji Port at 13:50 JST. The estimated wave height is 3 metres. At Miyako, local high tide is at 14:49 JST. At Kamaishi and Ofunato, high tide is at 14:53 JST — meaning waves arriving ahead of or during high tide will compound their destructive reach inland.

Iwate’s deeply indented ria coastline — the same geography that amplified the 2011 Tohoku tsunami to catastrophic heights at many of these exact locations — means that 3-metre open ocean estimates can translate to significantly higher run-up heights in bays and inlets. Miyako, Kamaishi and Ofunato are among the communities most severely affected by the 2011 disaster and have rebuilt with seawalls and evacuation infrastructure since then.

Aomori Prefecture’s Pacific Coast — Tsunami Warning, 3 Metres

Aomori’s Pacific-facing coastline is under a full 3-metre tsunami warning. Estimated wave arrivals cover Mutsuogawara Port at 13:50 JST with high tide at 14:40 JST, Hachinohe Port at 14:00 JST with high tide at 14:39 JST, and Mutsu City’s Sekinehama at 14:10 JST with high tide at 14:26 JST. Hachinohe is one of the region’s largest ports and most densely populated coastal cities in the warning zone.

Hokkaido’s Central Pacific Coast — Tsunami Warning, 3 Metres

Hokkaido’s central Pacific coast faces a 3-metre tsunami warning with waves estimated to arrive at Urakawa Town and Erimo Town’s Shono at 14:00 JST and Tokachi Port at 14:10 JST. High tide at Urakawa is at 14:47 JST, Tokachi Port at 14:42 JST and Erimo Town’s Shono at 14:28 JST — placing the tsunami arrival window dangerously close to high tide across all three observation points simultaneously.

Miyagi Prefecture — Tsunami Advisory, 1 Metre

Miyagi Prefecture is under a 1-metre tsunami advisory. Estimated arrivals cover Ishinomaki City’s Ayukawa at 14:10 JST with high tide at 15:01 JST, Ishinomaki Port at 14:30 JST with high tide at 14:59 JST, and Sendai Port at 14:40 JST with high tide at 15:01 JST. Sendai and Ishinomaki were among the hardest-hit cities in the 2011 disaster. Advisory-level waves at 1 metre can still cause dangerous conditions at river mouths and low-lying coastal areas.

Fukushima Prefecture — Tsunami Advisory, 1 Metre

Fukushima Prefecture faces a 1-metre advisory with waves arriving at Iwaki City’s Onahama Port at 14:30 JST with high tide at 15:18 JST, and Soma at 14:40 JST with high tide at 15:09 JST. Fukushima’s coastal communities, which include the area near the Fukushima Daiichi nuclear facility, are under close monitoring. No radiation-related alerts have been issued at this stage.

Hokkaido’s Eastern Pacific Coast — Tsunami Advisory, 1 Metre

The eastern Pacific coast of Hokkaido faces a 1-metre advisory covering Kushiro at 14:10 JST, Kiritappu Port in Hamanaka Town at 14:10 JST, Nemuro City’s Hanasaki at 14:20 JST and Nemuro Port at 14:40 JST. High tide at Nemuro Port is at 14:17 JST — meaning the wave could arrive slightly after high tide, which partially reduces but does not eliminate the compounding risk.

Hokkaido’s Western Pacific Coast — Tsunami Advisory, 1 Metre

Western Hokkaido’s Pacific coast is under a 1-metre advisory covering Shiraoi Port at 14:10 JST, Tomakomai West and East Ports at 14:20 JST, Hakodate at 14:30 JST, Muroran Port at 14:30 JST, Yoshioka in Fukushima Town at 14:40 JST and Mori Port in Oshima at 14:30 JST. High tide at Muroran is at 15:54 JST and at Mori Port at 15:59 JST — later than wave arrival, which slightly reduces the compounding risk at those specific points.

Aomori’s Sea of Japan Coast — Tsunami Advisory, 1 Metre

Aomori’s Sea of Japan-facing coast, which is on the opposite side of the Aomori Peninsula from the Pacific-facing communities already under warning, faces a 1-metre advisory. Tappi is estimated at 14:30 JST and Fukaura at 15:00 JST. This advisory reflects the propagation of tsunami energy around the northern tip of Honshu into the Sea of Japan — a less common but documented phenomenon in major Sanriku earthquakes.

The Shaking — Cities and Towns That Felt the Earthquake

Beyond the tsunami zones, the earthquake itself caused significant shaking across a vast geographic footprint. The strongest intensity of 5-plus was recorded in Hashikami Town, Aomori. Intensity 5-minus — strong enough to cause furniture movement, potential structural damage in older buildings and widespread fear — was felt in Hachinohe City and multiple Aomori towns, Miyako City, Morioka City and Hanamaki City in Iwate, and Tome City and Wakuya Town in Miyagi.

Intensity 4 shaking was recorded across dozens of cities including Sendai, Ishinomaki, Kesennuma, Kuji, Ofunato, Kamaishi, Odate, Akita, Hakodate in Hokkaido and multiple Fukushima communities. Intensity 3 was felt across Tokyo’s Hachioji City, Yokohama and multiple Kanagawa wards, Saitama, Chiba and across Niigata and Fukushima Prefectures. Lower-level shaking reached as far as Nagoya in Aichi, Toyama, Gifu, Shizuoka and Shiga Prefectures — an extraordinary geographic spread reflecting the earthquake’s shallow depth and high energy release.

What to Do If You Are in an Affected Area

Japan’s Meteorological Agency’s official guidance is unambiguous. Evacuate immediately to higher ground. Do not wait for visual confirmation of waves. Waves can arrive earlier or later than forecast. Waves can be significantly higher than estimated. Continue evacuating until all warnings and advisories are officially lifted. Stay away from coasts and river mouths that can overflow even under advisory-level conditions.

Business Upturn will continue updating this report as wave measurements, damage assessments and official bulletins are released by NHK and Japan’s Meteorological Agency.

Disclaimer: This article is based on NHK reports and Japan Meteorological Agency data. All figures and timings are subject to revision by Japanese authorities. Readers in affected areas must follow official Japanese government evacuation instructions without delay.