February 12, 2025
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On January 13, a magnitude (M) 6.6 earthquake occurred at a depth of about 35 km under the Hyuganada Sea. The earthquake caused the maximum seismic intensity 5 Lower and damage including some injured people were in Miyazaki Prefecture. Long-period ground motion class 2 was observed in Miyazaki and Kumamoto prefectures, and 23 cm tsunami was observed at the Miyazaki Port (Port and Harbors Bureau), and other tsunami were observed from Kochi to Kagoshima Prefectures.
* On January 23, an M5.2 earthquake occurred at a depth of about 5 km in Aizu, Fukushima Prefecture, with a maximum seismic intensity 5 Lower in Fukushima Prefecture.
There was no remarkable activity.
* On January 23, an M5.2 earthquake occurred at a depth of about 5 km in Aizu, Fukushima Prefecture. An M4.7 earthquake also occurred on the same day near the epicenter of this event. The focal mechanism of these earthquakes was a transverse strike-slip fault type with a compression axis in the NW-SE direction, and both earthquakes occurred in the crust. Seismic activity near the epicenter of this earthquake has been high since January 21, including 90 earthquakes with a seismic intensity 1 or over by February 11. Around the epicenter of this earthquake, earthquakes of M4.0 or over have sometimes occurred: an M6.3 earthquake (maximum seismic intensity 5 Upper) on February 25, 2013, with concentrated seismic activities at that time.
According to GNSS observations, no significant crustal deformation associated with this earthquake was observed.
* In the seismically active area of the M7.6 earthquake on January 1, 2024, seismic activity, which has been active since December 2020, is still ongoing, although overall seismic activity has been declining outside of the active area of the earthquake offshore west of Ishikawa Prefecture on November 26, 2024. There were 37 earthquakes of seismic intensity 1 or over from December 1 to 31 (29 events offshore west of Ishikawa Prefecture, including one with seismic intensity 3). The largest earthquake in December was an M4.4 earthquake (maximum seismic intensity 3) at 7:11 on December 24. Note that the number of earthquakes of seismic intensity 1 or over in November was 136 (123 events offshore west of Ishikawa Prefecture).
According to the GNSS observation, crustal deformations, which were considered to be post-seismic deformation, were observed in 12 months after the M7.6 earthquake on January 1: 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 6 cm in an WNW direction at the Suzu observatory and subsidence of about 9 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, 2,629 earthquakes with seismic intensity 1 or over occurred from December 1, 2020 to December 31, 2024. 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 January 13, an M6.6 earthquake occurred at a depth of about 35 km under the Hyuganada Sea. 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 at the boundary between the Philippine Sea plate and the continental plate. This earthquake caused tsunamis from Kochi to Kagoshima Prefectures, including a 23 cm tsunami at the Miyazaki Port (Port and Harbors Bureau).
The earthquake occurred within the active area after the M7.1 earthquake on August 8, 2024. Seismic activity was high immediately after the M7.1 earthquake, but the latest earthquake occurred while the number of earthquakes had been decreasing over time. Seismic activity has remained high since the M6.6 earthquake, including an M5.4 earthquake on the 15th, but the number of earthquakes has decreased as time has passed.
According to GNSS observations, crustal deformation was observed mainly in Miyazaki Prefecture, including a horizontal displacement of approximately 5 cm in the southeast direction and subsidence of approximately 2 cm at the Sadowara station. According to the seafloor geodetic observations with the GNSS-acoustic ranging combination technique, no significant crustal deformation was observed at several stations relatively close to the epicenter of the earthquake on January 13, 2025 before and after this earthquake.
Crustal deformations considered to be a post-seismic effect were observed mainly in southern Miyazaki Prefecture, including a displacement of 5 cm in the southeast direction at the Miyazaki station for about 5 months (until the M6.6 earthquake) after the M7.1 earthquake on August 8, 2024. Furthermore, crustal deformations considered to be a post-seismic effect were continuously observed after the M6.6 earthquake.
The earthquake source fault of this earthquake, inferred from the focal mechanism, distribution of seismic activity, GNSS observations, and seismic wave analysis, is adjacent to the northern part of the source fault of the M7.1 earthquake that occurred on August 8, 2024, and is located on a plate boundary.
Near the epicenter of the present earthquake, an M6.9 earthquake on October 19, 1996 and an M6.7 earthquake on December 3, 1996 occurred, both of which caused damage. The earthquake occurred in the area of "smaller interplate earthquakes of the Hyuganada Sea," which the Earthquake Research Committee had evaluated in its "Long-Term Evaluation of Seismic Activity of Hyuganada Sea and Nansei Islands Trench (Second Edition) (released on March 25, 2022)." The probability of an earthquake of M7.0 to M7.5 occurring within 30 years in this area is ranked III (#), which is classified as a group with a high probability of occurrence among subduction zone earthquakes.
* 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 January 21, an M6.1 earthquake occurred near Taiwan. The focal mechanism of this earthquake was of the type with a compression axis in the WNW-ESE direction.
#: Rank of the probability of occurrence of a subduction zone earthquake within 30 years is expressed as follows; rank: probability, III: greater than 26%, II: 3% ~ 26%, I: smaller than 3%, X: unknown (an immediate occurrence of an earthquake cannot be denied).
Note: GNSS is a general name of a satellite positioning system such as GPS.
February 12, 2025
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in January 2025 are as follows.
(Reference)
The following events for the period from January 2024 until the end of December 2024 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – In the Noto Region, Ishikawa Prefecture# | M7.6 on January 1, 2024 (Depth of approximately 15 km) |
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| – 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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# 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.
– Deep low-frequency earthquakes (tremors) have been observed near the boundary between the Philippine Sea plate and the continental plate from January 24 to February 3 in the Tokai to northern Kii Peninsula. According to strain and tilt data, slight crustal deformations were observed near the tremors almost synchronously with the deep low-frequency earthquakes (tremors). These are considered to be caused by short-term slow slip events at the deeper part of the boundary between the Philippine Sea plate and the continental plate.
– 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 appears to be continuing 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.
There is no supplementary information for Kyushu-Okinawa region.
– "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 February
7 (reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, February 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: