More than 150,000 people were instructed to move to evacuation centres, while those living close to the shoreline were told to leave beaches, harbours and low-lying waterfront districts without delay.
The warning was withdrawn several hours later after sea-level monitoring showed that a destructive tsunami had not developed. The US Pacific Tsunami Warning Center also said there was no threat to coastlines beyond Japan.
What is the difference between a tsunami warning, advisory and forecast in Japan?
Japan’s tsunami system is colour-coded. A yellow tsunami advisory is generally issued when waves of up to one metre are expected – which may sound relatively modest, but a one-metre surge can still create violent currents, sweep people from harbour walls or beaches and overturn small boats.
A red tsunami warning is meanwhile used when larger waves, generally of up to three metres, are possible. At that level, coastal and riverside districts may be inundated, and residents are expected to move quickly to higher ground or a designated refuge.
A purple major tsunami warning is the most serious category and indicates the possibility of waves exceeding three metres. These warnings are reserved for the kind of event capable of sweeping deep into coastal settlements and causing catastrophic damage.
The alert issued after the Kumamoto earthquake forecast waves of up to one metre for the Ariake and Yatsushiro seas.
Is it safe to travel to Japan right now?
For most visitors, yes. The earthquake has not affected Japan evenly, and there is no indication that trips to the country’s main tourist cities need to be cancelled across the board.
Tokyo lies more than 900 kilometres northeast of Kumamoto, while Kyoto and Osaka are several hundred kilometres away on the main island of Honshu. These cities remain outside the principal damage zone, and there have been no reports of widespread disruption to hotels, attractions or local transport there.
The situation is very different in Kumamoto and parts of central Kyushu. There, damaged roads, interrupted power supplies and suspended train services are likely to make travel difficult even in places where hotels themselves have escaped serious damage.
Travellers with plans elsewhere in Japan can continue as normal while keeping an eye on official updates. Those heading to Kyushu should check their exact route, as disruption may affect one city or railway line while another part of the island remains relatively unaffected.
Is it safe to travel to Kumamoto?
Travel to the most heavily affected parts of Kumamoto should be reconsidered while emergency work and inspections continue.
Kumamoto City and the surrounding towns are still being assessed for structural damage, and the disruption extends beyond the buildings visibly damaged in television footage.
The mountainous areas east of the city require particular care. Popular destinations such as Mount Aso, Kurokawa Onsen and the rural hot-spring towns of central Kyushu are reached by roads that cut across steep slopes, bridges and tunnels. Even where no major damage is apparent, landslides or rockfalls may force closures at short notice.
Are flights to Japan affected by the Kumamoto earthquake?
International flights to Tokyo, Osaka and most other Japanese gateways are operating outside the immediate impact zone, but air travel into Kumamoto has been disrupted.
AloJapan.com