April 11, 2022
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On March 16, there was a magnitude (M) 7.4 earthquake offshore Fukushima prefecture, and maximum seismic intensity 6 Upper was observed in Miyagi and Fukushima prefectures. In Miyagi prefecture long-period ground motion class 4 was observed. Also, some damage with fatalities was caused.
* On March 18, there was an M5.6 earthquake offshore Iwate prefecture. Maximum seismic intensity 5 Upper was observed in Iwate prefecture and damage with partially damaged houses was caused.
* On March 27, there was an M5.1 earthquake at a depth of approximately 55 km under the eastern Hidaka region (#1). 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.
* With regard to the earthquake offshore Fukushima prefecture on March 16, refer to another report (Evaluation of Earthquake Offshore Fukushima Prefecture on March 16, 2022).
* On March 18, there was an M5.6 earthquake at a depth of approximately 20 km, offshore Iwate prefecture. Also, in the vicinity of the recent event, on 30th there was an M4.9 earthquake. The focal mechanisms of these events showed a strike-slip fault type with a tension axis in an NNW-SSE direction. These events occurred within the continental plate.
According to the GNSS observation, no significant crustal deformation was observed associated with the recent event.
* 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 March 2022 and later: such as an M4.8 earthquake on March 8, two M4.3 earthquakes on March 23 and April 4, and an M4.2 earthquake on April 8 occurred. From March 1, 2022 till April 11 at 08:00 (JST) there occurred 33 earthquakes with seismic intensity 1 or over: 8 earthquakes with seismic intensity 3 or over. From December 1, 2020 till April 11, 2022 at 08:00 (JST) there occurred 115 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 March 31, there was an M4.7 earthquake at a depth of approximately 75 km under the Tokyo Bay (#2). The focal mechanism showed a reverse fault type with a compression axis in an E-W direction. This event occurred at the boundary between the Pacific and the Philippine Sea plates. In the vicinity of the recent event, on October 7, 2021, there was an M5.9 earthquake at the boundary between the Pacific and the Philippine Sea plates.
* On March 31, 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.
* Within the continental plate offshore northwest of Okinawa Main Island, an active seismic activity is observed from January 30 and till April 11 at 08:00 (JST), there occurred 36 earthquakes with seismic intensity 1 or over. From March 1 till April 11 at 08:00 (JST), there occurred 23 earthquakes. On February 9 an M5.6 earthquake, on February 22 an M5.8 earthquake, on March 17 the largest M5.9 earthquake and on March 30 an M5.5 earthquake occurred.
According to the GNSS observation, crustal deformation was observed from about February 2022 such as a southeastward displacement of 1 cm 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.
* On March 6, there was an M5.1 earthquake in the ocean near Amami Oshima.
* On March 19, there was an M5.9 earthquake at a depth of approximately 170 km, offshore northwest of Ishigakijima Island. The focal mechanism showed a strike-slip fault type with a compression axis in an NW-SE direction. The event occurred within the Philippine Sea plate.
* 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 March 23, there was an M6.6 earthquake at a depth of approximately 30 km (CMT solution) near Taiwan. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction.
* 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 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.
#1: [Southern Kushiro region] was the region name used in the announcement of JMA.
#2: [Northwestern Chiba prefecture] was the region name used in the announcement of JMA.
Note: GNSS is a general name of satellite positioning system such as GPS.
April 11, 2022
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during March 2022.
(Reference)
The following events for the period from March 2021 to late February 2022 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – In Kermadec Islands | Mw8.1 on March 5, 2021 | ||
| – In the Northern Wakayama Prefecture | M4.6 on March 15, 2021 (Depth of approximately 5 km) |
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| – Offshore Miyagi Prefecture | M6.9 on March 20, 2021 (Depth of approximately 60 km) |
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| – 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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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.
– 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.
– "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.":
(This evaluation is in agreement with the views presented at the regular meeting on April 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, April 7, 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: