April 10, 2026
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
* On March 8, at 22:08 and 22:17, and on March 14 and 26, earthquakes of magnitudes (M) 5.6, M6.1, M5.2, and M6.7, respectively, occurred offshore of Sanriku at a depth of approximately 15 km. The focal mechanisms suggest reverse faulting with the pressure axis oriented in the WNW-ESE direction. These earthquakes occurred at the boundary between the continental and Pacific Plates. Persistent seismic activity was observed near the focal areas, with 12 earthquakes of seismic intensity 1 or greater recorded in March.
Following the M5.3 earthquake on November 4, 2025, seismic activity in the focal areas surged and culminated in the M6.9 earthquake on November 9, 2025.
Furthermore, this series of earthquakes is accompanied by tremor activity.
* On March 10, an M4.7 earthquake occurred offshore of Fukushima Prefecture at a depth of approximately 60 km. The focal mechanism suggests reverse faulting with the pressure axis oriented in the ENE-WSW direction. This event occurred within the Pacific Plate.
* On March 2, an M6.2 earthquake occurred in the ocean near Ioto Island at a depth of approximately 20 km (according to the CMT solutions). The focal mechanism suggests normal faulting with a tension axis oriented in the NE-SW direction.
* On March 15, an M4.5 earthquake occurred in southern Gunma Prefecture at a depth of approximately 85 km. The focal mechanism showed a pressure axis oriented in the direction of the subducting Philippine Sea Plate. This suggests that the earthquake occurred within the Philippine Sea Plate.
There was no remarkable activity.
* On March 1, an M5.4 earthquake occurred offshore west of Satsuma Peninsula at a depth of approximately 120 km. The focal mechanism showed a tension axis oriented in the direction of the subducting Philippine Sea Plate. This suggests that the earthquake occurred within the Philippine Sea Plate.
* On March 15 and 21, earthquakes of M3.9 and M3.5, respectively, occurred in the Amakusa and Ashikita region, Kumamoto Prefecture at depths of approximately 5 km and 10 km. The focal mechanism of the March 21 event suggests strike-slip faulting with the tension axis oriented in the NW-SE direction. This event occurred in the crust.
Since March 15, seismic activity has surged within the focal areas of these earthquakes and is still ongoing. As of March 31, 51 earthquakes with seismic intensity 1 or greater were recorded.
This seismic activity zone is located close to the Hinagu Fault Zone (Yatsushiro Sea and Hinagu sections). According to long-term seismic evaluations by the Headquarters for Earthquake Research Promotion, the probability of an earthquake occurring in both sections within the next 30 years is rated as S* rank (high)#1.
To the northeast of this seismic activity zone lies the seismic activity zone of the "2016 Kumamoto Earthquakes#2,"which stretches from the Kumamoto region, Kumamoto Prefecture to the central Oita Prefecture. Since the "2016 Kumamoto Earthquakes," seismic activity in the Aso region, Kumamoto Prefecture, including the current activity zone, has remained more active than before.
* Starting February 26, seismic activity offshore northwest of Miyakojima Island surged. By March 31, a total of 32 earthquakes with seismic intensity 1 or greater had been recorded (17 of which occurred in March alone). These earthquakes took place within the continental plate. The largest event in the series was the M6.2 earthquake on March 2, characterized by a normal fault mechanism with a tension axis oriented in the NNW-SSE direction.
GNSS observations indicated that this was accompanied by slight crustal deformation.
* No unusual changes have been recorded that would suggest that the likelihood of a great earthquake occurring along the Nankai Trough has increased compared to that of a normal situation.
* On April 1, an M5.0 earthquake occurred in southern Ibaraki Prefecture at a depth of approximately 50 km. The focal mechanisms suggest reverse faulting with the pressure axis oriented in the NW-SE direction. This earthquake occurred at the boundary between the Philippine Sea Plate and the continental plate.
GNSS observations suggest that this earthquake was not accompanied by any significant crustal deformation.
Note: GNSS is a general name of a satellite positioning system such as GPS.
#1: For active faults, the probability of an earthquake occurring within the next 30 years is rated as follows: "S rank: greater than or equal to 3%, "A rank": 0.1% to less than 3%, "Z rank": less than 0.1%, and X rank": unknown (where it is difficult to assess the probability due to insufficient historical earthquake data). An asterisk (*) is appended to the rank for active faults with a post-seismic recurrence rate#3 of 0.7 or greater. Even for "Z rank" faults, the presence of an active fault indicates that there is still a possibility of a major earthquake occurring in the region.
#2: The "2016 Kumamoto Earthquakes" (as named by the Japan Meteorological Agency) refers to the series of seismic events centered on Kumamoto Prefecture that occurred on or after April 14, 2016, at 21:26.
#3: The elapsed time from the most recent seismic event to the evaluation point is divided by the average activity interval. When the time elapsed from the most recent earthquake to the evaluation point is equal to the average activity interval, the value will be 1.0.
April 10, 2026
Earthquake Research Committee
The numbers of earthquakes by magnitude (M) in and around Japan in March 2026 are as follows.
(Reference)
The following events for the period from March 2025 until the end of February 2026 have been listed as "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."
| – In northern Nagano Prefecture | M5.1 on April 18, 2025 (Depth of approximately 15 km) |
||
| – In the ocean near Tokara Islands | M5.3 on June 30, 2025 | ||
| – In the ocean near Tokara Islands | M5.1 on July 2, 2025 | ||
| – In the ocean near Tokara Islands | M5.6 on July 2, 2025 | ||
| – In the ocean near Tokara Islands | M5.5 on July 3, 2025 (Depth of approximately 10 km) |
||
| – In the ocean near Tokara Islands | M5.4 on July 5, 2025 | ||
| – In the ocean near Tokara Islands | M4.9 on July 6, 2025 | ||
| – In the ocean near Tokara Islands | M5.5 on July 6, 2025 | ||
| – In the ocean near Tokara Islands | M5.1 on July 7, 2025 | ||
| – Offshore east of the Kamchatka Peninsula, Russia | M8.8 on July30, 2025 | ||
| – In the ocean near Tokara Islands | M4.7 on September 17, 2025 | ||
| – Offshore southeast of the Nemuro Peninsula | M5.8 on October 25, 2025 (Depth of approximately 40 km) |
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| – Offshore of Sanriku | M6.9 on November 9, 2025 (Depth of approximately 15 km) | ||
| – In Aso region, Kumamoto Prefecture | M5.8 on November 25, 2025 (Depth of approximately 10 km) | ||
| – Offshore east of Aomori Prefecture | M7.5 on December 8, 2025 (Depth of approximately 55 km) | ||
| – In eastern Shimane Prefecture | M6.4 on January 6, 2026 (Depth of approximately 10 km) | ||
There is no supplementary information for Hokkaido region.
– GNSS observations show that, following the M7.5 earthquake that occurred offshore east of Aomori Prefecture on December 8, 2025, horizontal deformations believed to result from post-seismic deformation were observed primarily in Aomori Prefecture. At the Higashidori observation point, an eastward shift of approximately 3 cm was recorded over a period of about four months.
Additionally, since the occurrence of the M7.5 event, tremor activity has continued intermittently in the area east of the seismic activity zone.
– GNSS observations suggest that the crustal deformation differs from the usual trend in the area stretching from the western Shizuoka to the eastern Aichi Prefectures, a phenomenon observed since early 2022. This change is believed to be the result of a long-term slow slip occurring deep within the boundary between the Philippine Sea Plate and the continental plate, which extends from the Atsumi Peninsula to Lake Hamana. The slip center is gradually shifting from the Atsumi Peninsula towards Lake Hamana.
– From February 8 to February 26, March 1 to March 7, March 9 to March 10, and March 12 to March 16, deep low-frequency earthquakes (tremor activity) were recorded near the boundary between the Philippine Sea Plate and the continental plate in the central Kii Peninsula and the Tokai region. Strain and tilt data suggest that the slight crustal deformations recorded in the area were almost synchronized with the deep low-frequency earthquakes (tremors). It is believed that this phenomenon resulted from a short-term slow slip event occurring deep within the boundary between the two plates.
There is no supplementary information for Kyushu-Okinawa region.
– "No unusual changes have been recorded that would suggest
that the likelihood of a great earthquake occurring along the Nankai Trough
has increased compared to that of a normal situation.":
(This evaluation corroborates the views presented at the regular meeting
of the Nankai Trough Earthquake Assessment Committee on April 7 (reference
below).)
(Reference)
Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, April 7, 2026)
"In the present, no unusual changes have been recorded that would suggest that the likelihood of a great earthquake occurring along the Nankai Trough has increased compared to that of a normal situation. (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: