March 11, 2025
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
* On February 21, an earthquake of magnitude (M) 4.9 occurred at a depth of about 50 km offshore of Fukushima Prefecture. The earthquake had a focal mechanism of a reverse fault type with a compression axis in the WNW-ESE direction, and occurred at the boundary between the Pacific Plate and the continental plate.
* Seismic activity continues in the active zone of the M6.6 earthquake (maximum seismic intensity 6 Lower) offshore west of Ishikawa Prefecture on November 26, 2024, with an M4.9 earthquake (maximum seismic intensity 3) on February 24, 2025. Although seismic activity has been decreasing in the active area of the M7.6 earthquake in the Noto region, Ishikawa Prefecture on January 1, 2024, the activity, which has been high since December 2020, is still ongoing. There were 25 earthquakes of seismic intensity 1 or over from February 1 to 28 (18 events in the active area of the M 6.6 earthquake offshore west of Ishikawa Prefecture). The largest earthquake in January was an M4.1 earthquake (maximum seismic intensity 3) at 21:22 on January 16. Note that the number of earthquakes of seismic intensity 1 or over in January was 12 (5 events offshore west of Ishikawa Prefecture).
According to the GNSS observation, crustal deformations, which were considered to be post-seismic deformation, were observed in 14 months after the M7.6 earthquake on January 1, 2024: the horizontal displacements larger than 1 cm were observed in wide areas; in Toyama, Niigata, and Nagano Prefectures centering on the Noto Peninsula such as the displacement of about 7 cm in an WNW direction at the Suzu observatory and subsidence of about 10 cm at the Wajima observatory.
The number of earthquakes in the crust of the Noto region, Ishikawa Prefecture, has been increasing since around 2018. The seismic activity became high from December 2020: There was an M5.4 earthquake in June 2022, an M6.5 in May 2023, an M7.6 in January 2024, an M6.0 in June, and an M6.6 in November. In the series of seismic activities, 2,666 earthquakes with seismic intensity 1 or over occurred from December 1, 2020 to February 28, 2025. Crustal deformation has also been observed since December 2020.
Based on the seismic activity and crustal deformation to date, the series of seismic activity from December 2020 is considered to continue for the time being, and there is a possibility of future earthquakes with strong shaking and tsunamis in and around the active area after the M7.6 earthquake.
There was no remarkable activity.
* On February 4, an M5.2 earthquake occurred at a depth of about 30 km (according to the CMT solution) offshore northeast of Amami-Oshima. The focal mechanism of this earthquake was of a reverse fault type with a compression axis in the WNW-ESE direction, and the earthquake occurred within the Philippine Sea 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.
* On March 9, M5.8 and M5.9 earthquakes occurred offshore northeast of Amami-Oshima Island (*1). The focal mechanisms of these earthquakes have a NW-SE compression axis and a WNW-ESE compression axis type, respectively. Seismic activity near the epicenter of these earthquakes has been high since March 9, and there were 10 earthquakes of seismic intensity 1 or over observed by 09:00 on March 10.
*1: The place name of the epicenter used by the JMA in its information release was "under the ocean area near Amami-Oshima."
Note: GNSS is a general name of a satellite positioning system such as GPS.
March 11, 2025
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in February 2025 are as follows.
(Reference)
The following events for the period from February 2024 until the end of January 2025 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – Offshore of Fukushima Prefecture | M5.8 on March 15, 2024 (Depth of approximately 50 km) |
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| – Under Southern Ibaraki Prefecture | M5.3 on March 21, 2024 (Depth of approximately 45 km) |
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| – Under the Northern Coast of Iwate Prefecture | M6.0 on April 2, 2024 (Depth of approximately 70 km) |
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| – Near Taiwan | M7.7 on April 3, 2024 | ||
| – Offshore East of the Osumi Peninsula | M5.1 on April 8, 2024 (Depth of approximately 40 km) |
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| – Under the Bungosuido Strait | M6.6 on April 17, 2024 (Depth of approximately 40 km) |
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| – In the Noto Region, Ishikawa Prefecture# | M6.0 on June 3, 2024 (Depth of approximately 15 km) |
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| – 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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# Seismic activity of the 2024 Noto Peninsula Earthquakes
There is no supplementary information for Hokkaido region.
– Fourteen years have passed since the "the 2011 off the Pacific coast of Tohoku Earthquake" (hereinafter referred to as the Tohoku-Oki Earthquake), and overall, the seismic activity in the aftershock area is approaching the state before the Tohoku-Oki Earthquake. However, the number of earthquakes per year in the coastal areas is still larger than that before the Tohoku-Oki Earthquake, and the seismic activity of the present state will continue for the time being. According to the GNSS and the ocean-bottom crustal deformation observation, the crustal deformation, considered to be post-seismic deformation, is still observed in a wide area of eastern Japan and the seafloor in the aftershock area. Although the post-seismic deformation has become small over time, it has not yet returned to the state before the Tohoku-Oki Earthquake.
– 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.
– According to the GNSS observation, the crustal deformation different from the ordinary trend in the central Shikoku has been observed since about spring 2019. This phenomenon is considered to be caused by a long-term slow slip around the central Shikoku at the deeper part of the boundary between the Philippine Sea plate and the continental plate. This crustal deformation was temporally decaying since the fall of 2023 and appeared to continue from the spring of 2024 but slowed again in the fall of 2024.
– 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.
– According to GNSS observations, crustal deformation, considered to be post-seismic deformation, was observed mainly in the southern part of Miyazaki Prefecture for about five months (until the M6.6 earthquake on January 13, 2024) 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 1 cm in the southeast direction at the Miyazaki and Sadowara stations for about a month.
– "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 March 7 (reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, March 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: