(UPDATE) TOKYO — Japan has warned of a possible "megaquake" after eight people were injured Thursday by one of magnitude 7.1 in the south.

"The likelihood of a new major earthquake is higher than normal, but this is not an indication that a major earthquake will definitely occur," the Japan Meteorological Agency (JMA) said.

It was the first advisory issued under a new system drawn up following a major quake in 2011.

The JMA's "megaquake advisory" warned that "if a major earthquake were to occur in the future, strong shaking and large tsunamis would be generated."

"The likelihood of a new major earthquake is higher than normal, but this is not an indication that a major earthquake will definitely occur during a specific period of time," it added.

The advisory concerns the Nankai Trough "subduction zone" between two tectonic plates in the Pacific Ocean, where massive earthquakes have hit in the past.

The 800-kilometer undersea trough runs from Shizuoka, west of Tokyo, to the southern tip of Kyushu island.

It has been the site of destructive quakes of magnitude eight or nine every century or two.

These so-called "megathrust quakes," which often occur in pairs, have been known to unleash dangerous tsunamis along Japan's southern coast.

Meanwhile, Japanese Prime Minister Fumio Kishida said he has canceled a planned trip to Central Asia after earthquake scientists said the country should prepare for a possible "megaquake."

"As the prime minister with the highest responsibility for crisis management, I decided I should stay in Japan for at least a week," Kishida told reporters.

Traffic lights and cars shook and dishes fell off shelves during Thursday's tremor off the southern island of Kyushu, but no serious damage was reported.

The Fire and Disaster Management Agency said eight people were hurt — including several hit by falling objects.

Sitting on top of four major tectonic plates, the Japanese archipelago of 125 million people sees some 1,500 quakes every year, most of them minor.

Even with larger tremors, the impact is generally contained thanks to advanced building techniques and well-practiced emergency procedures.

'Risk elevated, but low'

"While earthquake prediction is impossible, the occurrence of one earthquake usually does raise the likelihood of another," experts from Earthquake Insights said.

They added that even when the risk of a second earthquake is elevated, it is "still always low."

On January 1, a 7.6-sized jolt and powerful aftershocks hit the Noto Peninsula on the Sea of Japan coast, killing at least 318 people, toppling buildings, and knocking out roads.

In 2011, a mammoth 9.0-magnitude undersea quake off northeastern Japan triggered a tsunami that left around 18,500 people dead or missing.

It sent three reactors into meltdown at the Fukushima nuclear plant, causing Japan's worst post-war disaster and the most serious nuclear accident since Chernobyl.