June 11, 2024
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
There was no remarkable activity.
* Although seismic activity around the focal region of the M7.6 earthquake on January 1 (JST, hereinafter the same time) in the Noto region, Ishikawa Prefecture has been decreasing, seismic activity, which has been high since December 2020, is still ongoing, including an M6.0 earthquake (maximum seismic intensity 5 Upper) occurring on June 3. The focal mechanism of the earthquake on June 3 was a reverse fault type with a compression axis in an NW-SE direction. There were 28 earthquakes with seismic intensity 1 or over (maximum seismic intensity: number of earthquakes, 4: 0, 3: 2) from May 1 to May 31. The largest earthquakes in May were M3.8 events at 18:50 (maximum seismic intensity 3) and 19:40 (maximum seismic intensity 1) on May 10. Note that there were 45 earthquakes with seismic intensity 1 or over in April.
In the case of major earthquakes in the continental plate, large earthquakes occurred while the number of earthquakes was gently decreasing such as the 2004 Mid Niigata prefecture Earthquake (M6.8), the 2016 Kumamoto Earthquakes (M7.3), and the 2018 Hokkaido Eastern Iburi Earthquake (M6.7).
The following crustal deformations considered to be post-seismic deformation were observed in the five months after the M7.6 earthquake on January 1: the horizontal displacements larger than 1 cm observed in wide areas, in Toyama, Niigata, and Nagano Prefectures centering on the Noto Peninsula such as the displacement of about 3 cm in an N-W direction at the Noto observatory and subsidence in the northern Noto Peninsula such as about 7 cm at the Wajima observatory. In addition, crustal deformation was observed following the M6.0 earthquake on June 3, including horizontal displacements of up to 2 cm and uplift of up to 3 cm around the epicenter of this earthquake.
In the offshores west, north, and northeast of the Noto Peninsula, several reverse faults dipping southeast with strikes generally in an NE-SW direction, are identified as active faults. Comparing high-resolution seismic reflection and bathymetry survey data acquired by AIST and the Japan Coast Guard after the 2024 earthquake in this area with equivalent pre-earthquake data, fault displacements with uplift of the southeast side relative to the northwest side were observed in a wide area along the active fault zone offshore northwest of the Noto Peninsula. Uplift of about 1 m was observed in the eastern part of the Monzen-oki segment of the active fault zone, 1 to 4 m in the Saruyama-oki segment, 1 to 3 m in the Wajima-oki segment, and about 2 m in the Suzu-oki segment. Furthermore, uplift of up to 3-4 m was newly identified in the Wajima-oki and the Suzu-oki segments. These uplifts are likely associated with the M7.6 earthquake on January 1 and are presumed to be caused by a displacement of the southeast-dipping reverse fault.
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 and even higher from July 2021. There were an M5.4 earthquake in June 2022, an M6.5 earthquake in May 2023 and an M7.6 earthquake in January 2024. In the series of seismic activity, 2,351 earthquakes with seismic intensity 1 or over occurred from December 1, 2020, to May 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 May 21, an M5.6 earthquake occurred at a depth of about 50 km (according to CMT solution) under the ocean near Chichijima Island. The focal mechanism of this earthquake was of the type with a compression axis in an ENE-WSW direction.
* On May 26, an M4.7 earthquake occurred at a depth of about 65 km under southern Ibaraki Prefecture. The focal mechanism of this earthquake was a reverse fault type with a compression axis in an E-W direction, and it occurred at the boundary between the Pacific and the Philippine Sea Plates.
There was no remarkable activity.
* On May 31, an M4.7 earthquake occurred at a depth of about 15 km in the Kumamoto region, Kumamoto Prefecture. The focal mechanism of this earthquake was of the type with a tension axis in an N-S direction. This event occurred within the 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.
* On May 10, an M6.5 earthquake occurred near Taiwan. The focal mechanism of this earthquake was a reverse fault type with a compression axis in an NE-SW direction.
* On June 1, an M4.5 earthquake occurred at a depth of about 40 km under the Bungosuido Strait. The focal mechanism of this earthquake was of the type with a tension axis in an E-W direction. This event occurred within the Pacific Plate.
Note: GNSS is a general name of a satellite positioning system such as GPS.
June 11, 2024
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in May 2024 are as follows.
(Reference)
The following events for the period from May 2023 until the end of April 2024 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – Offshore of the Noto Peninsula# | M6.5 on May 5, 2023 (Depth of approximately 10 km) |
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| – Under the Southern Chiba Prefecture | M5.2 on May 11, 2023 (Depth of approximately 10 km) |
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| – In the Ocean Area near Tokara Islands (Near Kuchinoshima and Nakanoshima Islands) |
M5.1 on May 13, 2023 | ||
| – In the Ocean Area near Niijima and Kozushima Islands | M5.3 on May 22, 2023 (Depth of approximately 10 km) |
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| – Offshore East of Chiba Prefecture | M6.2 on May 26, 2023 (Depth of approximately 50 km) |
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| – Offshore of Tomakomai | M6.2 on June 11, 2023 (Depth of approximately 140 km) |
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| – 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) |
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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) | ||
# 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 from 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 and the continental plates. This crustal deformation was temporally decaying since the fall of 2023, but appears to have continued recently.
– Seismic activity has been decreasing since the M6.6 earthquake on April 17 under the Bungosuido Strait. There were 82 earthquakes with seismic intensity 1 or over (maximum seismic intensity: number of earthquakes, 6 Lower: 1, 4: 2) from 23:00 on April 17 to 09:00 on June 10.
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 on June 7 of the Assessment Committee for Earthquakes Along the Nankai Trough (reference below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, June 7, 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: