A series of earthquakes has been shaking the seas near the Tokara islands in Kagoshima Prefecture since Saturday, with Japan’s Meteorological Agency warning that seismic activity remains elevated and could continue for some time.

As of 2 p.m. on Monday, more than 200 earthquakes registering shindo 1 or higher on the Japanese seismic intensity scale had been observed. Of these, three registered shindo 4, 15 reached shindo 3, and more than 100 were shindo 1. The strongest quake so far was a magnitude 5.2 event recorded at around 5 p.m. on Sunday that caused shaking measured at shindo 4 on Akuseki Island in the village of Toshima, which comprises 12 islands located between Okinawa and the Kyushu region.

No tsunami has been reported in connection with any of the quakes.

According to the Meteorological Agency, the tremors began around 5 a.m. on Saturday as weak earthquakes below shindo 1 that were barely felt on the ground. By 8 a.m., quakes strong enough to be felt by residents began increasing in frequency, particularly between Akuseki and the small neighboring Kodakara Island. The epicenters have been closer to Kodakara, although the strongest tremors were recorded on Akuseki.

“This region is known for repeated bursts of seismic activity,” said Masashi Kiyomoto, a Meteorological Agency official in charge of earthquakes and tsunamis, noting that similar clusters occurred in December 2021 and September 2023.

In the 2023 series, 346 quakes of shindo 1 or greater were recorded, and in 2021, 308 events were logged, including a magnitude 6.1 quake that reached shindo 5 on Akuseki.

The earthquakes are thought to occur within the continental plate at a shallow depth, Kiyomoto said, but noted that the exact cause remains unclear and there are no undersea volcanoes or active faults in the region.

“Based on past patterns, this could continue for about a month. While it’s not known whether it will completely calm down, the strongest activity tends to occur within the first one to two weeks,” Kiyomoto added.

While there has been no tsunami so far, authorities warn that a larger event — such as one at magnitude 6 or higher — could heighten the risk.

“Past events haven’t reached that level, but if a stronger quake does occur, tsunami threats cannot be ruled out,” Kiyomoto said.

The agency is urging residents in the Tokara islands — especially on Akuseki, Kodakara, and nearby Takara Island — to remain on alert.

“We encourage people to stay in safe places, secure furniture, and be prepared to evacuate if necessary,” he said. “Please pay close attention to earthquake and tsunami information as the situation develops.”

As of May 31, the population of all the seven inhabited islands of Tokara is 669 people, according to the Toshima Village Hall website.