April 9, 2025
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
There was no remarkable activity.
* On March 19, a magnitude (M) 4.7 earthquake occurred offshore of the Noto Peninsula at a depth of approximately 5 km. The fault mechanism involved reverse faulting with a northwest-southeast pressure axis. This event occurred in the seismic activity zone of the M7.6 earthquake that struck the Noto region, Ishikawa Prefecture on January 1, 2024.
While seismic activity in the activity zone of the M7.6 earthquake has been decreasing, however, the ongoing activity from December 2020 persists. Notably, the occurrence of the M6.6 earthquake (maximum seismic intensity 5 Lower) offshore west of Ishikawa Prefecture on November 26, 2024. Between March 1 and March 31, 12 earthquakes with a seismic intensity 1 or greater have occurred, including 4 events in the seismic activity zone of the M6.6 earthquake offshore west of Ishikawa Prefecture. Throughout February, 25 earthquakes with a seismic intensity 1 or greater also occurred, including 18 events offshore west of Ishikawa Prefecture.
GNSS observations indicate that during the 14 months following the January 1, M7.6 earthquake, a horizontal deformation of about 7 cm in the west-northwest direction was recorded at the Suzu observatory and a horizontal deformation exceeding 1 cm across a wide area centered on the Noto Peninsula–affecting Toyama, Niigata, and Nagano prefectures. At the Wajima observatory, a subsidence of about 10 cm was recorded. These crustal deformations are attributed to the effects of afterslip.
Since 2018, the number of earthquakes in the Noto region, Ishikawa Prefecture has been on the rise, with a notable increase in seismic activity starting in December 2020. This includes the M5.4 earthquake in June 2022, the M6.5 earthquake in May 2023, the M7.6 earthquake in January 2024 and, the M6.0, and M6.6 earthquakes in June and November 2024, respectively. From December 1, 2020 to March 31, 2025, a total of 2,678 earthquakes with a seismic intensity 1 or greater were recorded, along with crustal deformation observed around December 2020.
From the current status of seismic activity and crustal deformation, a series of earthquake activity from December 2020 is expected to continue for the time being. There is also a possibility of future earthquakes in the affected area and the surroundings following the M7.6 earthquake; potentially accompanied by strong shaking and tsunamis.
There was no remarkable activity.
* On March 9, two earthquakes, M5.8 and M5.9, occurred offshore northeast of Amami-Oshima Island (#1), at depths of approximately 10 km and 20 km, respectively (according to CMT solutions). The focal mechanisms of these earthquakes displayed a pressure axis oriented in the NW-SE and WNW-ESE direction, respectively. The seismic activity near the epicenters slightly increased between March 9 and 11, but the overall number of earthquakes has gradually decreased. By March 31, a total of 12 seismic events with a seismic intensity 1 or greater had been recorded.
* On March 18, an M4.8 earthquake struck at a depth of about 10 km in the Kumamoto region, Kumamoto Prefecture (#2). The earthquake's focal mechanism revealed a tension axis oriented in the north-south direction and occurred within the earth's crust.
* 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.
#1: The place name of the epicenter used by the JMA's information released about the M5.8 earthquake was the "ocean area near Amami-Oshima."
#2: The place name of the epicenter used by the JMA's information released was the "Amakusa-Ashikita region, Kumamoto Prefecture."
Note: GNSS is a general name of a satellite positioning system such as GPS.
April 9, 2025
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in March 2025 are as follows.
(Reference)
The following events for the period from March 2024 until the end of February 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.
There is no supplementary information for Tohoku region.
– 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 April 7
(reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, April 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: