May 13, 2022
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On April 19, there was a magnitude (M) 5.4 earthquake under the northern Ibaraki prefecture (#). Maximum seismic intensity 5 Lower was observed in Ibaraki prefecture.
* On April 24, there was an M5.4 earthquake at a depth of approximately 25 km, offshore Tokachi. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On April 4, there was an M5.4 earthquake at a depth of approximately 45 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On April 6, there was an M5.2 earthquake at a depth of approximately 55 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred within the Pacific plate.
In the vicinity of the recent event, on March 16, 2022 there was an M7.4 earthquake within the Pacific plate. The aftershock activity still continues, but is decaying: from March 16 till May 12 at 08 o'clock (JST), there occurred 132 earthquakes with seismic intensity 1 or over: of these, there occurred 25 earthquakes from April 1 till May 12 at 08 o'clock (JST).
* In the crust of the Noto region, Ishikawa prefecture, where the number of earthquakes is increasing since about 2018, the seismic activity became high since December 2020, and it has become higher since about July 2021. The largest is an M5.1 earthquake which occurred on September 16, 2021. The high seismic activity continues in April 2022 and later: such as an M4.3 earthquake on April 4, and an M4.2 earthquake on April 8. From April 1 till May 12 at 08 o'clock (JST) there occurred 19 earthquakes with seismic intensity 1 or over: of these 4 earthquakes with seismic intensity 3 or over. From December 1, 2020 till May 12, 2022 at 08:00 (JST) there occurred 123 earthquakes with seismic intensity 1 or over.
According to the GNSS observation, since about December 2020, the following crustal deformation has been observed in the Noto Peninsula: the cumulative displacement of 1 cm over in the south-southwest direction at the Noto observatory in Noto Town, Ishikawa prefecture, and the uplift of 3 cm over at the Suzu observatory in Suzu City.
Based on the situation of the seismic activity and the crustal deformation, the series of the seismic activity will continue for the time being.
* On April 2, there was an M4.4 earthquake at a depth of approximately 55 km under the northern Ibaraki prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On April 4, there was an M4.6 earthquake at a depth of approximately 60 km under the northwestern Chiba prefecture. The focal mechanism had a tension axis in an NW-SE direction. This event occurred within the Philippine Sea plate.
* On April 7, there was an M4.7 earthquake at a depth of approximately 10 km in the eastern Aichi prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an E-W direction. This event occurred within the crust.
* On April 19, there was an M5.4 earthquake at a depth of approximately 95 km under the northern Ibaraki prefecture (#). The focal mechanism had a compression axis in an ENE-WSW direction. This event occurred within the Pacific plate.
According to the GNSS observation, no significant crustal deformation was observed accompanying the recent event.
* On April 6, there was an M3.6 earthquake at a depth of approximately 5 km in the northern Wakayama prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an WNW-ESE direction. The event occurred within the crust.
* Within the continental plate offshore northwest of Okinawa Main Island, an active seismic activity is observed from January 30 and till May 12 at 08 o'clock (JST), there occurred 48 earthquakes with seismic intensity 1 or over. From April 1 till May 12 at 08 o'clock (JST), there occurred 18 earthquakes. In the series of seismic activity, till April 30 there occurred 11 earthquakes of M5.0 or over, the largest being an M5.9 on March 17. The largest in April is an M5.6 on 13th.
According to the GNSS observation, crustal deformation was observed from about February 2022 such as a south-southeastward displacement of 1 cm or so of Gushikawa observatory, Kumejima Town, Okinawa prefecture.
In the neighborhood of the area of the recent seismic activity, there were several seismic clusters: from February to March 1980 and in August 2007, there were clusters including earthquakes of M6.0 or over. In the seismic activity from February to March 1980, there were M6.7 and M6.3 earthquakes.
* There has been observed no unusual change which indicates that the possibility of occurrence of great earthquakes along the Nankai Trough has relatively raised compared to the normal time.
* On April 24, there was an M6.2 earthquake in Kuril Islands. In the vicinity of the recent event, in April there occurred 39 earthquakes of M4.0 or over.
* On May 2, there was an M5.0 earthquake at a depth of approximately 20 km in the Hyuganada. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On May 2, there was an M4.4 earthquake at a depth of approximately 15 km in the southern Kyoto prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an E-W direction. The event occurred within the crust. In the vicinity of the recent event, the seismic activity became high since March 31: on March 31 occurred an M4.4 earthquake, and on April 30 occurred an M4.3 earthquake. From March 31 till May 12 at 08 o'clock (JST), there occurred 14 earthquakes with seismic intensity 1 or over: of these, 4 earthquakes with seismic intensity 3 or over.
In the neighborhood of the recent seismic activity, there was a cluster from February to March, 1999: an M4.2 on February 12 and an M4.0 on March 12.
* On May 3, there was an M4.6 earthquake at a depth of approximately 130 km under the eastern Tama, Tokyo prefecture. The focal mechanism had a compression axis in an NNE-SSW direction. This event occurred within the Pacific plate.
* On May 5, there was an M4.8 earthquake at a depth of approximately 50 km under the southern Ibaraki prefecture. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On May 9, there was an M6.6 earthquake at a depth of approximately 20 km in the ocean near Yonagunijima Island. The focal mechanism had a compression axis in an NNW-SSE direction.
In the vicinity of the recent event there are several cases in which earthquakes of similar scale consecutively occurred: on April 20, 2015 there was an M6.8 earthquake and after 10 hours occurred an M6.4 earthquake.
#: [Nakadori, Fukushima prefecture] was the region name used in the announcement of JMA.
Note: GNSS is a general name of satellite positioning system such as GPS.
May 13, 2022
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during April 2022
(Reference)
The following events for the period from April 2021 to late March 2022 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Offshore Miyagi Prefecture | M6.8 on May 1, 2021 (Depth of approximately 50 km) |
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| – In the Noto Region, Ishikawa Prefecture | M5.1 on September 16, 2021 (Depth of approximately 15 km) |
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| – Offshore Iwate Prefecture | M5.9 on October 6, 2021 (Depth of approximately 55 km) |
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| – Under the Northwestern Chiba Prefecture | M5.9 on October 7, 2021 (Depth of approximately 75 km) |
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– Under the Eastern and Fujigoko Regions, |
M4.8 on December 3, 2021 Regions, Yamanashi prefecture |
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| – Under the Kii Channel | M5.4 on December 3, 2021 (Depth of approximately 20 km) |
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| – In the Ocean near Tokara Islands | M6.1 on December 9, 2021 | ||
| – Under the Ocean near Chichijima Island | M6.1 on January 4, 2022 (Depth of approximately 60 km) |
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| – Under the Hyuganada |
M6.6 on January 22, 2022 (Depth of approximately 45 km) |
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| – Offshore Fukushima Prefecture | M7.4 on March 16, 2022 (Depth of approximately 55 km) |
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| – Under the Hyuganada | M5.6 on March 18, 2022 (Depth of approximately 20 km) |
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There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
There is no supplementary information for Kanto-Chubu region.
– In the area extending from the central to western Shikoku, from March 29 to April 13, deep low-frequency earthquakes (tremors) were observed, near the boundary between the Philippine Sea and the continental plates. According to the strain, inclination, and GNSS data, in the surroundings, slight crustal deformation was observed, almost synchronized with deep low-frequency earthquakes (tremors). These phenomena are considered to be caused by the short-term slow-slip at 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 from 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.
– According to the GNSS observation, the crustal deformation different from the ordinary trend in the western Kii Peninsula and the eastern Shikoku has been observed from about summer 2020. This phenomenon is considered to be caused by a long-term slow-slip around the Kii Channel 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 southern Kyushu, being observed from about summer 2020, is considered to be caused by a long-term slow-slip around the southern Hyuganada at the deeper part of the boundary between the Philippine Sea and the continental plates. Recently this crustal deformation seems to be stagnant.
– "here has been observed no unusual change which indicates that the possibility of occurrence of great earthquakes along the Nankai Trough has relatively raised compared to the normal time.":
(This evaluation is in agreement with the views presented at the regular
meeting on May 11 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, May 11, 2022)
"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 raised compared to the normal time. (Excerpted)"
There is no supplementary information for other regions.
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: