Shinkansen bullet-train service was suspended in some areas while engineers checked for any damage to the tracks.
No abnormalities were detected at the Higashidori or Onagawa nuclear power plants, operator Tohoku Electric Power said.
The JMA warned people to be cautious of further quakes of a similar intensity for about a week.
“Additionally, there is a possibility of even stronger earthquakes occurring, so please stay alert,” it said.
Geologists Kyle Bradley and Judith A Hubbard said that there was no way to tell whether a strong earthquake will be followed by a similarly strong, or even stronger, one.
“Instead, we must rely on historical statistics, which tell us that very few large earthquakes are soon followed by even larger events,” they said in their Earthquake Insights newsletter.
“It does happen, just not very often.”
“MEGAQUAKE”
In 2011, a magnitude-9.0 quake triggered a tsunami that left 18,500 people dead or missing and caused a devastating meltdown at the Fukushima nuclear plant.
Japan sits on top of four major tectonic plates along the western edge of the Pacific “Ring of Fire” and is one of the world’s most tectonically active countries.
The archipelago, home to around 125 million people, experiences around 1,500 jolts every year.
The vast majority are mild, although the damage they cause varies according to their location and depth below the Earth’s surface.
Quakes are extremely hard to predict, but in January, a government panel marginally increased the probability of a major jolt in the Nankai Trough off Japan in the next 30 years to 75 to 82 per cent.
The government then released a new estimate in March saying that such a “megaquake” and subsequent tsunami could cause as many as 298,000 deaths and damages of up to US$2 trillion.
