Strong Kanto Quake Injures Dozens, Triggering Warnings of Similar Shaking Over Next Week

A magnitude 5.9 earthquake struck Tokyo and the wider Kanto region at around 2 a.m. on Sunday, August 23, injuring at least 37 people and disrupting rail service across the densely populated metropolitan area. Japan's weather agency has warned residents to remain vigilant for the possibility of similarly strong shaking over the coming week.

Where and How Strong the Shaking Was

The earthquake's epicenter was in southern Ibaraki Prefecture, at a depth of roughly 68 to 70 kilometers. The Japan Meteorological Agency put the magnitude at 5.9, while the US Geological Survey measured it slightly lower, at 5.8. The shaking reached lower 5 on Japan's seven-point shindo intensity scale in Tokyo's Adachi Ward and in parts of Ibaraki, Saitama, and Chiba prefectures — a level the agency says can cause objects to fall off shelves and force people to grab onto something to steady themselves. Level 4 shaking was recorded elsewhere in Tokyo, as well as in Tochigi, Gunma, and Kanagawa prefectures. In some areas, the shaking lasted up to a full minute.

Casualties and Damage

According to NHK, at least nine people were injured in Saitama Prefecture and another eight in Kanagawa Prefecture. In the city of Ushiku in Ibaraki Prefecture, part of a ceiling collapsed inside the city hall building. Minor injuries and reports of people becoming trapped in elevators were also recorded in Tokyo. No tsunami warning was issued, and there were no reports of deaths or serious structural damage.

Woken by Emergency Alerts

The shaking struck shortly after earthquake early-warning alarms sounded on mobile phones nationwide, jolting many residents awake around 2 a.m. Long-period ground motion — a slower, more prolonged type of shaking that can cause high-rise buildings to sway significantly — was recorded at Level 2 across Tokyo's 23 wards, as well as in Saitama and Chiba prefectures. At that level, the Japan Meteorological Agency notes people may have difficulty standing, and furniture or other objects can move or fall, even in buildings far from the epicenter.

Transit Disruptions

The earthquake disrupted rail service across the region. JR East reported delays on numerous lines Sunday morning, including the Joban Line, Keihin-Tohoku Line, Shonan-Shinjuku Line, Musashino Line, Chuo-Sobu Line, and Sotobo Line, among others serving the greater Kanto area.

Government Response

Prime Minister Sanae Takaichi wrote on X within an hour of the quake that efforts to assess the extent of damage were underway, and that a liaison office had been established at the Prime Minister's Office Crisis Management Center. She said she had issued instructions to relevant officials to prioritize public safety and gather accurate information on the quake's impact.

The Warning for the Week Ahead

The Japan Meteorological Agency urged residents in areas that experienced strong shaking to remain vigilant for the possibility of another earthquake of similar magnitude over the coming week — a standard precautionary advisory Japanese authorities typically issue following moderate-to-strong seismic events, given the elevated likelihood of aftershocks in the days that follow a significant quake.

Part of a Difficult Stretch for Japan's Seismic Activity

Sunday's earthquake comes less than a month after a far more devastating magnitude 7.1 earthquake struck the Kumamoto region on the southern island of Kyushu, killing 38 people, injuring 364, and destroying more than 1,500 buildings outright while damaging nearly 20,000 more. By comparison, Sunday's Kanto quake caused no deaths and no serious structural damage — though its proximity to the densely populated Tokyo metropolitan area meant it woke and alarmed a far larger number of people than the more powerful but more remote Kumamoto quake. Separately, the Japanese government announced Saturday it would roll out tourism support measures, including a travel discount campaign, for the Kyushu region still recovering from that earlier disaster.

Why Japan Is So Prone to Earthquakes

Japan sits at the junction of four tectonic plates and records thousands of measurable earthquakes every year, the vast majority of which go unnoticed by the public. Buildings across the country are constructed to strict seismic standards precisely because of how frequently events like this occur — a key reason Sunday's magnitude-5.9 quake, despite briefly disrupting daily life for millions, resulted in no deaths and no major structural failures.

What's Next

With the weather agency's advisory in effect through the coming week, residents across Tokyo and the wider Kanto region are being urged to stay alert for potential aftershocks or further seismic activity of similar strength. For continuing coverage, see The Japan Times' report.