August 12, 2025
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On July 3, a magnitude (M) M5.5 earthquake occurred in the ocean near Tokara Islands (near Kodakarajima Island), it recorded a maximum seismic intensity 6 Lower in Toshima Village, Kagoshima Prefecture. Seismic activity in the area has increased since June 21. In addition to the M5.5 event, six other earthquakes with a maximum intensity 5 Lower or greater were recorded in July.
* On July 30, an M8.8 earthquake struck offshore east of the Kamchatka Peninsula, Russia, resulting in tsunamis that were observed along a vast area of the Pacific coast, from Hokkaido to Okinawa. The earthquake led to casualties and other damage.
* On July 28, an M5.2 earthquake occurred in the southern Tokachi region at a depth of approximately 50 km. This earthquake occurred at the plate boundary between the Pacific and continental plates and was associated with reverse faulting, with the pressure axis oriented in an NW-SE direction.
There was no remarkable activity.
* On July 15, an M4.9 earthquake occurred in northern Ibaraki Prefecture at a depth of approximately 55 km. This earthquake occurred at the plate boundary between the Pacific and continental plates and was associated with reverse faulting, with the pressure axis oriented in an NW-SE direction.
There was no remarkable activity.
* On July 3, an M5.5 earthquake (maximum seismic intensity 6 Lower) occurred in the ocean near Tokara Islands (near Kodakarajima Island) at a depth of approximately 10 km. The earthquake occurred within the continental plate and was associated with a strike-slip faulting, with the tension axis oriented in an NNW-SSE direction. Since June 21, intense seismic activity has been observed in the region surrounding the epicenter (the area from Akusekijima Island to Takarajima Island). Between June 21 and the end of July, a total of 2,238 earthquakes with a seismic intensity 1 or greater (including 8 earthquakes with a maximum seismic intensity 5 Lower or greater) were recorded. The strongest shock in the series was the M5.6 that occurred on July 2.
GNSS observations indicate that horizontal displacement occurred alongside seismic activity. At the Takarajima observation point, a shift of approximately 2 cm to the east-northeast was recorded from the onset of seismic activity until just before the largest earthquake (M5.6 on July 2). At the time of the M5.6 earthquake, this displacement was about 4 cm to the south. In contrast, at Kodakarajima Island, the displacement direction shifted from northeast to north-northwest. Since July 4, the Takarajima observation point has resumed shifting in the same direction as at the beginning of the seismic activity, whereas slight crustal deformations have also been recorded at Kodakarajima and Akusekijima Islands.
Since around July 20th, seismic activity has been decreasing, along with the number of large earthquakes. However, the current level of seismicity (seismic intensity 1 or greater occurring several times a day) may persist for some time.
Additionally, there have been instances in the past where active seismic activity persisted for several months in the area surrounding the current seismic activity zone. For example, in April 2021, seismic activity continued for several months before declining. After several more months, activity resumed again in December.
* On July 25, an M4.8 earthquake occurred in southwestern Nagasaki Prefecture at a depth of approximately 10 km. The quake occurred within the continental plate and was associated with a tension axis mechanism oriented in an N-S direction.
* There has been observed no unusual change which indicates that the possibility of occurrence of a great earthquake along the Nankai Trough has relatively risen compared to the normal time.
* On July 30, an M8.8 earthquake occurred offshore east of the Kamchatka Peninsula, Russia. It triggered a tsunami that was observed along a vast area of the Pacific coast, from Hokkaido to Okinawa Prefecture, including a 1.4 m tsunami (preliminary measurement) at Kuji Port (Ministry of Land, Infrastructure, Transport and Tourism), Iwate Prefecture. This earthquake occurred at the plate boundary between the Pacific and North American plates and was associated with reverse faulting, with the pressure axis oriented in an NW-SE direction. On July 20, an M7.5 earthquake occurred near its epicenter.
GNSS observations show that after the M8.8 earthquake, a slight crustal deformation was recorded in northern Hokkaido. Furthermore, analysis from synthetic aperture radar interferometry using data from the Land Observation Technology Satellite "Daichi 2" revealed deformations exceeding 1 m in the southern Kamchatka Peninsula.
Historically, earthquakes with an M8.0 or greater have occurred offshore east of the Kamchatka Peninsula. Notable examples include an M8.4 earthquake in 1923 and an M9.0 earthquake in 1952. In November 2006, an M8.3 intraplate earthquake struck east of Kuril Islands, followed by an M8.1 earthquake in the outer rise about two months later, in January 2007. These seismic events generated tsunamis that were recorded across Japan.
Note: GNSS is a general name of a satellite positioning system such as GPS.
August 12, 2025
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in July 2025 are as follows.
Of the above monthly totals, the number of earthquakes in the ocean near Tokara Islands was 83, 14, and 0 for M4.0 or greater, M5.0 or greater, and M6.0 or greater, respectively.
(Reference)
The following events for the period from July 2024 until the end of June 2025 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – Under the Hyuganada Sea | M7.1 on August 8, 2024 (Depth of approximately 30 km) |
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| – In western Kanagawa Prefecture | M5.3 on August 9, 2024 (Depth of approximately 15 km) |
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| – In the northern Ibaraki Prefecture | M5.1 on August 19, 2024 (Depth of approximately 10 km) |
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| – In the Ocean Area near Torishima Island | M5.8 on September 24 (Depth of approximately 10 km) |
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| – Offshore west of Ishikawa Prefecture# | M6.6 on November 26, 2024 (Depth of approximately 10 km) |
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| – Under the Hyuganada Sea | M6.6 on January 13, 2025 (Depth of approximately 35 km) |
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| – In Aizu, Fukushima Prefecture | M5.2 on January 23, 2025 (Depth of approximately 5 km) |
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| – In northern Nagano Prefecture | M5.1 on April 18, 2025 (Depth of approximately 15 km) |
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# Seismic activity of the 2024 Noto Peninsula Earthquakes
There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
– Seismic activity in the Noto region of Ishikawa Prefecture has been on the rise since December 2020. Initially, only relatively small earthquakes were recorded; however, this changed with the occurrence of several large events, including an M6.5 earthquake in May 2023, an M7.6 earthquake in January 2024, and an M6.6 earthquake in November 2024. In the activity area of the M7.6 earthquake, seismic activity has been decreasing, yet 6 earthquakes with seismic intensity 1 or greater were recorded in July, suggesting that seismic activity is still ongoing.
GNSS observations indicate that crustal deformation, including horizontal deformation exceeding 2 cm over a 19-month period, was still detected in a broad area centered on the Noto Peninsula and extending into Toyama, Niigata, and Nagano prefectures following the M7.6 earthquake. This deformation is believed to be an after-slip effect.
Along the Sea of Japan, earthquakes with an M6.0 or greater have been recorded several years after major seismic events, such as the 1983 Sea of Japan earthquake (M7.7). Moreover, the Noto Peninsula has experienced large, damaging earthquakes of magnitude M6.0 or greater, including the Noto Hanto Earthquake in 2007 (M6.9), which occurred prior to the current series of seismic activities that began in December 2020.
– According to the GNSS observation, the crustal deformation different from the ordinary trend in the area extending from the western Shizuoka to the eastern Aichi Prefectures has been observed since early 2022. This phenomenon is considered to be caused by a long-term slow slip around the Atsumi Peninsula at the deeper part of the boundary between the Philippine Sea and the continental plates.
– From July 5 to July 10 and again from July 13 to July 22, deep low-frequency earthquakes (tremors) were recorded near the boundary between the Philippine Sea Plate and the continental plate in the Tokai region. Strain and tilt data suggest that the recorded slight crustal deformation was nearly synchronized with these tremors. This activity is believed to be linked to short-term slow slip at the boundary between the two plates.
– GNSS observations indicate that since spring 2019, central Shikoku has experienced crustal deformations that deviate from previous trends. This change is believed to result from long-term slow slip occurring deep within the boundary between the Philippine Sea Plate and the continental plate surrounding central Shikoku. Recently, these crustal deformations have ceased.
– According to GNSS observations, crustal deformation different from the previous trend has been observed in the southern Kii Peninsula since the beginning of 2020. This seems to be caused by long-term slow slip at the deep boundary between the Philippine Sea Plate and the continental plate around the southern Kii Peninsula. This deformation has been stagnant since the fall of 2024, but has been observed again since early 2025.
– Starting in February 2025, a series of tremors were recorded in northern Yamaguchi Prefecture; however, this activity has been decreasing since June. Additionally, GNSS and tiltmeters have detected slight crustal deformations associated with these seismic events.
– From June 7 to July 14, deep low-frequency earthquakes (tremors) were recorded near the boundary between the Philippine Sea Plate and the continental plate, spanning from western to eastern Shikoku. Strain and tilt data suggest that slight crustal deformation has been observed in the surrounding area, nearly synchronized with tremors activity. This activity is believed to be linked to short-term slow slip at the boundary between the two plates.
– According to GNSS observations, crustal deformation, considered to be post-seismic deformation, was observed mainly in the southern part of Miyazaki Prefecture for about six months (until the M6.6 earthquake on January 13, 2025) following the M7.1 earthquake under the Hyuganada Sea on August 8, 2024, including a horizontal displacement of about 5 cm to the southeast at the Miyazaki observatory. In addition, after the M6.6 earthquake, crustal deformations, considered post-seismic deformation, were also observed, including horizontal displacement of about 3 cm in the southeast direction at the Miyazaki station for about five months.
– On July 8, seismic activity in the ocean near Tokara Islands (near Suwanosejima Island), experienced a temporary increase. By the end of the month, a total of 33 earthquakes with a seismic intensity 1 or greater had been recorded (6 earthquakes with maximum seismic intensity 3 and 6 with maximum seismic intensity 2). The largest one was an M4.1 event that occurred at 5:34 a.m. on the 8th. All these earthquakes occurred within the continental plate.
– "There has been observed no unusual change which indicates that the possibility of occurrence of a great earthquake along the Nankai Trough has relatively risen compared to the normal time.":
(This evaluation is in agreement with the views presented at the regular meeting of the Nankai Trough Earthquake Assessment Committee on August 7 (reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, August 7, 2025)
"In the present, there has been observed no unusual change which indicates that the possibility of occurrence of great earthquakes along the Nankai Trough has relatively risen compared to the normal time. (Excerpted)"
Reference 1
Earthquakes that are described in the "Evaluation of Seismic Activity" (Monthly Report of Seismic Activity in Japan) have the following features.
Reference 2
Information that is described in the "Supplementary Information to the Evaluation" includes: