More than 1,000 Earthquakes Observed around Tokara Islands in Kagoshima Pref.; Highest Number in 10-Day Span

The Yomiuri Shimbun

18:42 JST, July 3, 2025

More than 1,000 earthquakes measuring 1 or stronger on the Japanese seismic intensity scale — including one that measured lower 6 — have hit areas around the Tokara Islands in Kagoshima Prefecture since June 21, the Japan Meteorological Agency said on Thursday.

According to the agency, the number of earthquakes since June 21 reached 1,031 as of 4 p.m. on Thursday.

At around 4:13 p.m. on Thursday, an earthquake with an estimated magnitude of 5.5 hit the Tokara Islands, according to the agency. It measured lower 6 on the intensity scale with a maximum of 7 at Akusekijima Island in Toshima in the prefecture.

Earlier on Thursday, the island was rocked by several earthquakes measuring 4 on the scale at 6:51 a.m., 2:31 p.m., 3:11 p.m., 3:18 p.m. and 3:35 p.m.

The government upgraded the information liaison office in the crisis management center of the Prime Minister’s Office to the countermeasures office on Thursday afternoon after the earthquake measuring lower 6 hit the island.

“Based on the prime minister’s directive, we are making all-out efforts to assess the damage and take emergency measures, including lifesaving and rescue, under the policy of ‘human life first,’” Chief Cabinet Secretary Yoshimasa Hayashi said at a press conference held after the major earthquake occurred. “We will work closely with local governments to implement these measures. Please be careful about the possible recurrence of earthquakes with an intensity level of lower 6.”

Many earthquakes have been occurring for about two weeks. There is a risk of falling rocks and cliff collapses in areas where the tremors were strong.

On Wednesday, the agency held an emergency press conference concerning the spate of earthquakes, calling on residents in the area to prepare for immediate evacuation.

This area has been repeatedly hit by earthquakes in the past. According to the agency, 308 earthquakes of an intensity 1 or higher were observed in December 2021 and 346 in September 2023. They mostly subsided over the course of a few days.

This time, the number of tremors has continued to increase for more than 10 days,

According to Hiroshi Yakiwara, associate professor of seismology at Kagoshima University and an expert on earthquakes in the Tokara Islands, the Philippine Sea plate is subducting under the Eurasian plate on the east side of the islands, and on their west side, there is an east-west spreading force centered on the Okinawa Trough.

“The pushing and subducting forces may be causing strain to accumulate in the surrounding faults, resulting in frequent earthquakes,” Yakiwara said.

He also said that unlike past earthquakes, the location of the focuses of the recent earthquakes have tended to gradually spread out into the surrounding areas, and it is possible that “fluids” such as water are rising under the seafloor, making the faults easier to slide.

As for the impact on a possible earthquake along the Nankai Trough, Yakiwara said, “There is no relation [between the recent quakes and a Nankai Trough quake] because the focus areas are far away.”