November 12, 2024
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
* On October 18, an M5.4 earthquake occurred at a depth of about 40 km, offshore of Iwate Prefecture. 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 Pacific and the continental plates.
* Although seismic activity in the focal region of the M7.6 earthquake on January 1 in the Noto region, Ishikawa Prefecture has been decreasing, seismic activity, which has been high since December 2020, is still ongoing. There were 14 earthquakes with seismic intensity 1 or over (maximum seismic intensity: number of earthquakes, 2: 6) from October 1 to October 31. The largest earthquake in October was the M4.3 event (maximum seismic intensity 2) at 20:19 on October 9. Note that there were 18 earthquakes with seismic intensity 1 or over in September.
According to the GNSS observation, following crustal deformations, which were considered to be post-seismic deformation, were observed in 10 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 5 cm in an NW direction at the Hegurajima observatory and subsidence in the northern Noto Peninsula such as about 8 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, and an M6.0 in June 2024. In the series of seismic activities, 2,456 earthquakes with seismic intensity 1 or over occurred from December 1, 2020 to October 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.
* On October 14, an M4.5 earthquake occurred at a depth of about 70 km under Tokyo Bay (*1). The focal mechanism of this earthquake was of a reverse fault type with a compression axis in the EW direction, and the earthquake occurred at the boundary between the Pacific and the Philippine Sea plates.
There was no remarkable activity.
There was no remarkable activity.
* 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 in its information release was "northwestern Chiba Prefecture."
Note: GNSS is a general name of a satellite positioning system such as GPS.
November 12, 2024
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in October 2024 are as follows.
(Reference)
The following events for the period from October 2023 until the end of September 2024 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – In the Ocean Area near Torishima Island | Maximum M6.5 October 2 ~ 9, 2023 | ||
| – in Mindanao, the Philippine Islands | Mw7.5 on December 2, 2023 | ||
| – In the Noto Region, Ishikawa Prefecture# | M7.6 on January 1, 2024 (Depth of approximately 15 km) |
||
| – Offshore of Fukushima Prefecture | M5.8 on March 15, 2024 (Depth of approximately 50 km) |
||
| – Under Southern Ibaraki Prefecture | M5.3 on March 21, 2024 (Depth of approximately 45 km) |
||
| – 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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# 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 fall 2023, but appears to have continued recently.
– In northern Wakayama Prefecture, there were rather high seismic activities from around 7:00 on 23 October, including 12 earthquakes with seismic intensity 1 or over and one event with 3 or over from October 23 to 31. The largest of these earthquakes was an M4.0 earthquake (maximum seismic intensity 3) at 7:08 am on October 23. The focal mechanism of this earthquake was of the type with a compression axis in the WNW-ESE direction, and the earthquake occurred in the crust. The number of earthquakes has been decreasing over time.
High seismic activities have been constantly observed around the current active region. There have been continuous high seismic activities in the past, including 25 earthquakes of seismic intensity 1 or over in February 2021, recently.
– According to GNSS observations, crustal deformation considered to be post-seismic deformation was observed mainly in the southern part of Miyazaki Prefecture, including a southeastward displacement of about 4 cm at the Miyazaki station during about three months after the M7.1 earthquake on August 8, 2024.
– "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 on November 8 of the Nankai Trough Earthquake Assessment Committee (reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, November 8, 2024)
"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: