Story highlights Tsunami advisories are canceled; "slight sea-level change" possible, agency says

The quake struck offshore some 80 miles east of Namie

The USGS puts the quake's magnitude at 6.5; Japan agency says 6.8

TEPCO spokesperson: All is normal at the Fukushima nuclear facility

A powerful earthquake struck early Saturday off the coast of northern Japan -- rattling nerves in a region rocked three years ago by a deadly tremor, tsunami and nuclear crisis, though thankfully the latest episode didn't nearly measure up.

The Japan Meteorological Agency at one point issued a tsunami warning, which it later amended to tsunami advisories for coastal regions in Iwate, Miyagi and Fukushima prefectures. The latter is the site of the Fukushima Daiichi nuclear power facility that was the center of a weeks-long radioactive crisis.

But a large tsunami never materialized.

At 6:15 a.m. Saturday (5:15 p.m. ET Friday), the same agency noted that all tsunami advisories had been canceled.

Whereas before the JMA urged everyone to "get out of the water and leave the coast immediately," that last update was less alarming. "Pay attention when fishing, swimming or engaging in other activities," the agency noted, "as there may still be slight sea-level changes for the time being."

The Japan Meteorological Agency characterized the quake as a 6.8-magnitude. Yet the U.S. Geological Survey had it a little weaker, downgrading its earlier estimate in calling it a 6.5-magnitude tremor.

According to the USGS, the quake was centered off Honshu island some 129 kilometers (79 miles) east-southeast of Namie and 284 kilometers east-northeast of Tokyo. It was 11 kilometers, or 7 miles, deep.

There were no immediate reports of damage.

Any sizable tremor in or near Japan -- and any tsunami warning -- inevitably raises dark memories dating to March 11, 2011, when a 9.0-magnitude struck 231 miles northeast of Tokyo.

That quake, the fourth largest on record since 1900 and the largest ever to hit Japan, produced a tsunami with 30-foot waves

When all was over, the combination of the quake and, especially, the tsunami left some 16,000 people dead.

The event also set off a prolonged crisis at the Fukushima Daiichi nuclear power plant in the northern part of Honshu, including the spread of some radioactive material and very real fears of an even worse calamity as authorities tried to bring the dangerous situation under control.

A repeat of that situation seemed unlikely after the early Saturday earthquake.

A spokesperson for TEPCO, the utility company that controls the Fukushima Daiichi facility, told CNN there were no disruptions to operations at the plant and that everything was operating normally.