Japan has lifted all tsunami warnings and advisories issued after Monday’s powerful 7.7-magnitude earthquake, with the highest tsunami waves recorded at around 80cm in Iwate prefecture on the east coast.

Authorities warned that the risk of another, even more powerful earthquake would remain for up to a week, with the likelihood of a magnitude 8.0 or higher megaquake “higher than during normal times”.

Monday’s tremor struck at 4.53pm local time (7.53am GMT) off the northeastern coast of Japan’s Sanriku and 330 miles (530km) from the country’s capital, Tokyo, with an epicentre in the Pacific Ocean measured at a depth of around 20km.

It prompted the Japanese Meteorological Agency to issue tsunami warnings, the second-highest alert capable of being issued, along swathes of the country’s coast – meaning waves of between one and three metres were originally expected.

Warnings were later downgraded to “advisories”, meaning swells of up to one metre were predicted. By midnight local time, all warnings and advisories were lifted.

No deaths or major damage were reported, but 100 homes were left without power, Japan’s government spokesperson Minoru Kihara told a news conference in Tokyo on Monday.

More than 170,000 people were advised to evacuate across several prefectures when the tsunami warnings and advisories were initially issued, although those evacuation orders have since been lifted.

Local media reported a number of people suffered minor injuries during evacuations, including elderly residents who fell and sustained fractures.

According to Mainichi, an elderly woman in her 80s was injured while evacuating her home in Urakawa in Hokkaido prefecture, likely fracturing her arm. An octogenarian man also reportedly broke his leg in a supermarket car park in Morioka in Iwate prefecture, while a woman in her 20s in Aomori prefecture’s Tohoku region suffered a head injury after hitting a chair.

On Monday, bullet train services were halted for several hours before resuming later in the evening, and some motorways were closed due to the tremors, which are reported to have been felt as far away as Tokyo.

The government has recommended people have a go-bag ready and check their preparations are in order amid the warning of a heightened risk of a megaquake.

The Japan Meteorological Agency (JMA) said that the chances of a larger earthquake of magnitude 8 or greater were 10 times higher than usual.

Normal predictions measure the chances of an earthquake at around a 0.1 per cent probability, but on Monday, the chances were one per cent.

“Please take anti-disaster steps, while embracing the idea that one must protect one’s own life,” a government official urged the public.

Witnesses described the scene at the coast on Monday afternoon as the tsunami warnings were issued. “Right now, local authorities are using loudspeakers in the neighbourhood to warn people about a possible tsunami and to stay alert,” Chaw Su Thwe, a Myanmar national residing in Hokkaido, told the BBC. “Office workers have been allowed to leave work early.”

Japan’s prime minister, Sanae Takaichi, said the government had set up an emergency taskforce ⁠and urged citizens in the affected areas to heed evacuation orders.

Broadcaster ⁠NHK showed ships sailing ‌out of Hachinohe port in Hokkaido in anticipation of the waves, as an alert reading “Tsunami! Evacuate!” flashed across the screen to inform viewers.

Emergency alert app NERV, on Monday, advised people to stay away from the coast and to avoid large bodies of water until the advisories were no longer in place.

The incident will trigger memories of the devastating 2011 Tohoku earthquake and tsunami, which killed 18,000 people and caused a meltdown at the Fukushima nuclear plant. Fukushima was one of the prefectures affected by a lower-level tsunami advisory on Monday.

The International Atomic Energy Agency (IAEA) said that no abnormalities had been observed at Japan’s nuclear facilities following the earthquake.

Japan is situated within the “Ring of Fire” of volcanoes and oceanic trenches, which partly encircle the Pacific Basin. It is one of the world’s most earthquake-prone countries, with tremors recorded at least every five minutes.

Around 20 per cent of the world’s earthquakes recorded at a magnitude of six or higher are recorded in Japan.