December 10, 2024
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On November 26, an M6.6 earthquake occurred at a depth of about 10 km offshore west of Ishikawa Prefecture. This earthquake caused a maximum seismic intensity 5 Lower in Ishikawa Prefecture and damage including injuries. A long-period ground motion class 2 was observed in Ishikawa Prefecture.
There was no remarkable activity.
* On November 16, an M4.6 earthquake occurred at a depth of about 10 km in Mutsu Bay. Another M5.1 earthquake occurred near the hypocenter of this earthquake on November 20. The focal mechanism of these earthquakes was of a reverse fault type with a compression axis in the ENE-WSW direction, and they occurred in the crust. The area around the epicenter of this earthquake was seismically active, with nine earthquakes of seismic intensity 1 or over occurring from November 16 to 30.
* On November 24, an M5.0 earthquake occurred offshore of Iwate Prefecture at a depth of about 40 km. The focal mechanism of this earthquake has a WNW-ESE compression axis, and the earthquake occurred at the boundary between the Pacific Plate and the continental plate.
* On November 26, an M5.4 earthquake occurred offshore of Miyagi Prefecture at a depth of about 40 km. The focal mechanism of this earthquake was of a reverse fault type with a compression axis in the WNW-ESE direction, and the event occurred at the boundary between the Pacific Plate and the continental plate.
* On November 26, an M6.6 earthquake occurred at a depth of about 10 km offshore west of Ishikawa Prefecture. The focal mechanism of this earthquake was of a reverse fault type with an EW compression axis, and the earthquake occurred within the crust. This earthquake occurred at the western edge of the seismically active zone following the M7.6 earthquake that struck the Noto region of Ishikawa Prefecture on January 1. After this earthquake, seismic activity has been high within about 20 km range in a NW direction, including an M4.7 earthquake on the 28th. There were 123 earthquakes of seismic intensity 1 or over from November 26 to 30 (maximum seismic intensity: number of earthquakes, 5 Lower: 1, 4: 1, 3: 5). Since the M7.6 earthquake on January 1 in the Noto region of Ishikawa Prefecture, high seismic activities have been sometimes observed near the hypocenter of this earthquake, including M4.0 earthquakes on January 3, February 1, and February 5, and an M3.8 earthquake on October 8. Following the M6.6 earthquakes, crustal deformation of about 1 cm to the west was observed around the Noto Peninsula. The Hakui-Oki Nishi fault and other faults are located near the seismically active area of this earthquake.
In the seismically active area of the M7.6 earthquake on January 1, 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 on November 26. There were 13 earthquakes with seismic intensity 1 or over from November 1 to 30, other than the seismic activity on November 26. Note that there were 14 earthquakes with seismic intensity 1 or over in October (4 events offshore west of Ishikawa Prefecture).
According to the GNSS observation, crustal deformations, which were considered to be post-seismic deformation, were observed in 11 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 Suzu observatory and subsidence of 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, an M6.0 in June, and an M6.6 in November. The M6.6 earthquake on November 26 was the second largest in a series of ongoing seismic activity since 2020. In the series of seismic activities, 2,592 earthquakes with seismic intensity 1 or over occurred from December 1, 2020 to November 2024. Crustal deformation has also been observed since December 2020.
A comparison of the seafloor topography of Toyama Bay surveyed in 2024 and 2010 showed that the slope of the seafloor valley offshore of Fushiki, Takaoka City, collapsed over an area of approximately 3 km from north to south and 0.5 km from east to west, and deepened by up to 10 m in addition to the submarine canyon offshore of Toyama City. This collapse is possibly related to the tsunami observed at the Fushiki Tide Station two minutes after the M7.6 earthquake.
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 November 7, an M6.3 earthquake occurred at a depth of about 10 km (according to the CMT solution) in the ocean area near Ioto Island. The focal mechanism of this earthquake was of a reverse fault type with an E-W compression axis. The hypocenter area of this earthquake had been seismically active since August, with 18 earthquakes of M5.0 or over occurring in November.
There was no remarkable activity.
* On November 17, an M5.9 earthquake occurred offshore northeast of Amami-Oshima Island at a depth of about 30 km (according to CMT solution). The focal mechanism of this earthquake has a WNW-ESE tension axis, and the earthquake occurred within the Philippine Sea Plate.
* On November 30, an M5.8 earthquake occurred in the ocean area near Miyakojima Island at a depth of about 40 km (according to the CMT solution). The focal mechanism of this earthquake was of a reverse fault type with a compression axis in the ENE-WSW 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 November 11, an M6.0 earthquake occurred at a depth of about 10 km (according to the CMT solution) in the Mariana Islands. The focal mechanism of this earthquake was of the type with an NE-SW compression axis, and the earthquake occurred within the Philippine Sea Plate.
Note: GNSS is a general name of a satellite positioning system such as GPS.
December 10, 2024
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in November 2024 are as follows.
Of the above monthly counts, 85, 18, and 1 earthquakes occurred in the
ocean area near Ioto Island for M4.0, M5.0, and M6.0 or over, respectively,
and 21, 2, and 1 earthquakes occurred offshore west of Ishikawa Prefecture,
respectively.
Although the number of earthquakes occurring during this period is high,
they have been observed once every one to two years.
(Reference)
The following events for the period from November 2023 until the end of October 2024 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – 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) |
||
| – 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) |
||
| – Under the Bungosuido Strait | M6.6 on April 17, 2024 (Depth of approximately 40 km) |
||
| – In the Noto Region, Ishikawa Prefecture# | M6.0 on June 3, 2024 (Depth of approximately 15 km) |
||
| – Under the Hyuganada Sea | M7.1 on August 8, 2024 (Depth of approximately 30 km) |
||
| – In western Kanagawa Prefecture | M5.3 on August 9, 2024 (Depth of approximately 15 km) |
||
| – In the northern Ibaraki Prefecture | M5.1 on August 19, 2024 (Depth of approximately 10 km) |
||
| – In the Ocean Area near Torishima Island | M5.8 on September 24 (Depth of approximately 10 km) |
||
# 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 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.
– According to GNSS observations, crustal deformation considered to be post-seismic deformation is observed mainly in the southern part of Miyazaki Prefecture, including a southeastward displacement of about 4 cm at the Miyazaki station during about 4 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: