March 10, 2026
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion

Evaluation of Seismic Activities for February 2026

1 Major Seismic Activities

There was no remarkable activity.

• Seismic Activity Across Japan in February 2026 (Magnitude 4.0 or Greater)

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2 Seismic Activities by Region

(1) Hokkaido Region

* On February 12, a magnitude (M) 5.2 earthquake occurred offshore east of Hokkaido. The focal mechanism shows reverse faulting, with the pressure axis oriented in the WNW-ESE direction.

• Hokkaido Region
• Earthquake Offshore East of Hokkaido on February 12

to supplementary reports

(2) Tohoku Region

* On February 20, an M5.1 earthquake occurred offshore east of Aomori Prefecture at a depth of approximately 55 km. The focal mechanism shows reverse faulting, with the pressure axis oriented in the WNW-ESE direction. This earthquake occurred at the boundary between the continental and Pacific Plates.
Following the M7.5 event on December 8, 2025, seismic activity in the focal areas surged. Throughout February, a total of 8 earthquakes with seismic intensity 1 or greater were recorded. This activity mainly increased near the epicenter of the M6.9 earthquake on December 12, 2025. Furthermore, tremor activity has been detected since February in areas to the east of the seismic activity zone.
According to GNSS observations, within approximately 3 months following the M7.5 quake, horizontal deformations, likely caused by post-seismic activity, were primarily detected in Aomori Prefecture. Notably, at the Higashidori observation point, an eastward shift of about 3 cm was recorded.

* On February 25, an M4.6 earthquake occurred in the northern coast of Iwate Prefecture at a depth of approximately 55 km. The focal mechanism shows a strike-slip faulting, with the pressure axis oriented in the E-W direction and occurred within Pacific Plates.

• Tohoku Region
• Earthquake Offshore East of Aomori Prefecture on February 20 (Seismic Activity Offshore East of Aomori Prefecture Since December 8, 2025)
• Earthquake Offshore East of Aomori Prefecture on February 20 (Seismic Activity Offshore East of Aomori Prefecture Since December 8, 2025) (continued)
• Earthquake Offshore East of Aomori Prefecture on February 20 (Seismic Activity Offshore East of Aomori Prefecture Since December 8, 2025) (continued)
• Offshore East of Aomori Prefecture on February 20 (Seismic Activity Following the M7.5 Earthquake on December 8, 2025)
• Seismic Activity Offshore East of Aomori Prefecture, Offshore of Iwate Prefecture, and Offshore of Sanriku
• Tremor Activity Offshore of Tokachi and Sanriku Before and After the Earthquake Offshore East of Aomori Prefecture on December 8, 2025, at 23:15
• GNSS Observation Data After the Earthquake Offshore East of Aomori Prefecture (M7.5, December 8) (provisional)
• GNSS Observation Data After the Earthquake Offshore East of Aomori Prefecture (M7.5, December 8) (provisional) (continued)
• GNSS Observation Data After the Earthquake Offshore East of Aomori Prefecture (M7.5, December 8) (provisional) (continued)
• Earthquake in the Northern Coast of Iwate Prefecture on February 25

to supplementary reports

(3) Kanto-Chubu Region

There was no remarkable activity.

• Kanto - Chubu Region

to supplementary reports

(4) Kinki-Chugoku-Shikoku Region

There was no remarkable activity.

• Kinki-Chugoku-Shikoku Region

to supplementary reports

(5) Kyushu-Okinawa Region

* On February 5, an M5.5 earthquake occurred offshore northeast of Amami-Oshima Island. The focal mechanism shows a reverse faulting, with the pressure axis oriented in the NW-SE direction. Additionally, on February 18, an M4.8 earthquake occurred near the epicenter.

• Kyushu Region
• Earthquake Offshore Northeast of Amami-Oshima Island on February 5
• Okinawa Region

to supplementary reports

(6) Around the Nankai Trough

* 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.

• Vertical Movement of GNSS-Based Control Stations - Omaezaki
• Vertical Movements of GNSS-Based Control Stations - the Kii Peninsula and Around Cape Muroto -

to supplementary reports

(7) Other Regions

* On February 22, an M6.1 earthquake occurred in the Kuril Islands.

• Earthquake in the Kuril Islands on February 22

Note: GNSS is a general name of a satellite positioning system such as GPS.

Supplementary Information to the Evaluation of Seismic Activities for February 2026

March 10, 2026
Earthquake Research Committee

1 Major Seismic Activities

The numbers of earthquakes by magnitude (M) in and around Japan in February 2026 are as follows.

• M4.0 or greater: 144 (137 events in January)
• M5.0 or greater: 22 (25 events in January)
• M6.0 or greater: 1 (3 events in January)

(Reference)

• M4.0 or greater: 81 / month (69-104)
• (Median monthly number from 1998 to 2017, half of the numbers are included in the interval shown in parentheses)
• M5.0 or greater: 10 / month (7-14)
• (Median monthly number from 1973 to 2017, half of the numbers are included in the interval shown in parentheses)
• M6.0 or greater: 1 / month (0-2)
• (Median monthly number from 1919 to 2017, half of the numbers are included in the interval shown in parentheses)
• M6.0 or greater: 16 / year (12-21)
• (Median annual number from 1919 to 2017, half of the numbers are included in the interval shown in parentheses)

The following events for the period from February 2025 until the end of January 2026 have been listed as "Major Seismic Activities "Major Seismic Activities" in the monthly "Evaluation of Seismic Activities."

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2 Nationwide Seismic Activities by Region

(1) Hokkaido Region

There is no supplementary information for Hokkaido region.

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(2) Tohoku Region

– In the aftershock zone of the "2011 off the Pacific coast of Tohoku Earthquake" (hereafter referred to as the "Tohoku Earthquake"), there are areas where seismic activity has temporarily increased. For example, the M6.9 earthquake that occurred offshore of Sanriku on November 9, 2025. Overall, however, seismic activity within the aftershock zone is gradually returning to pre-Tohoku Earthquake levels. The annual number of earthquakes occurring in coastal areas remains higher than before the Tohoku Earthquake, and seismic activity at this level is expected to continue in the foreseeable future. Furthermore, GNSS observations and seafloor crustal deformation monitoring indicate that crustal deformation is still occurring across a large area of eastern Japan and on the seafloor within the aftershock zone, likely caused by postseismic activity. Although post-seismic deformation has decreased over time, it has not yet returned to pre-Tohoku earthquake levels.

• About the "2011 off the Pacific coast of Tohoku Earthquake": 15 Years of Seismic Activity
• About the "2011 off the Pacific coast of Tohoku Earthquake": 15 Years of Seismic Activity (continued)
• About the" 2011 off the Pacific coast of Tohoku Earthquake": 15 Years of Seismic Activity (continued)
• About the "2011 off the Pacific coast of Tohoku Earthquake": 15 Years of Seismic Activity (continued)
• Crustal Deformation Before and After the 2011 Tohoku Earthquake
• Crustal Deformation Before and After the 2011 Tohoku Earthquake (continued)
• Crustal Deformation Before and After the 2011 Tohoku Earthquake (continued)
• Crustal Deformation Before and After the 2011 Tohoku Earthquake (continued)
• Crustal Deformation Before and After the 2011 Tohoku Earthquake (continued)
• Crustal Deformation Before and After the 2011 Tohoku Earthquake (continued)
• Seafloor Crustal Deformation Velocity After the 2011 Tohoku Earthquake as Determined by GNSS-A Observations
• GNSS-A Observations and Time-Dependent Displacement Velocity Offshore of Tohoku

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(3) Kanto-Chubu Region

- According to the GNSS observations, the crustal deformation differs from the ordinary trend for the area extending from the western Shizuoka to the eastern Aichi Prefectures has been observed since early 2022. This change is believed to result from long-term slow slip occurring deep within the boundary between the Philippine Sea Plate and the continental plate extending from the Atsumi Peninsula to Lake Hamana. The slip center is gradually shifting from the Atsumi Peninsula toward Lake Hamana.

• Coordinate Time Series (Black Circles) and Calculated Values (Red Lines) of Observing Stations in Tokai Region
• Long-Term Slow Slip in Tokai Region Estimated from GNSS Data (provisional)

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(4) Kinki-Chugoku-Shikoku Region

– From February 8 to 26, deep low-frequency earthquakes (tremor activity) were observed near the boundary between the Philippine Sea Plate and the continental plate from the northern and central Kii Peninsula. Strain and tilt data indicate that the slight crustal deformations observed around the area were almost synchronized with the deep low-frequency seismic activity (tremors). It is believed that this phenomenon resulted from a short-term slow slip event occurring deep at the boundary between the Philippine Sea Plate and the continental plate.

• Deep Low-Frequency Earthquake (Tremor) Activity and Short-Term Slow Slip from Northern to Central Kii Peninsula
• Short-Term Slow Slip Recorded from Northern to Central Kii Peninsula (February 9-26)
• Short-Term Slow Slip Recorded from Northern to Central Kii Peninsula (February 9-26) (continued)
• Short-Term Slow Slip Recorded from Northern to Central Kii Peninsula (February 9-26) (continued)
• Status of Deep Low-Frequency Earthquake Activity in the Kii Peninsula and Tokai Region (February 2026)
• Short-Term SSE Analysis Results for the Kii Peninsula (February 2026)
• Short-Term SSE Analysis Results for the Kii Peninsula (February 2026) (continued)
• Short-Term SSE Analysis Results for the Kii Peninsula (February 2026) (continued)

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(5) Kyushu-Okinawa Region

– From February 26 onwards, there was a surge in seismic activity offshore northwest of Miyakojima Island. By March 5, 28 earthquakes with seismic intensity 1 or greater were recorded (17 of which occurred in February alone). These earthquakes occurred within the continental plate. The largest was the M6.2 event on March 2. The focal mechanism shows a normal faulting, with the tension axis oriented in the NNW-SSE direction.
GNSS observations have revealed crustal deformation linked to this series of seismic activity.

• Seismic Activity Offshore Northwest of Miyakojima Island
• Earthquake Activity Offshore Northwest of Miyakojima Island (Past Earthquake Activity in the Okinawa Trough)
• Earthquake Activity Offshore Northwest of Miyakojima Island (Past Earthquake Activity in the Okinawa Trough) (continued)
• Crustal Deformation Associated with Seismic Activity Offshore Northwest of Miyakojima Island (provisional)
• Crustal Deformation Associated with Seismic Activity Offshore Northwest of Miyakojima Island (provisional) (continued)

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(6) Around the Nankai Trough

– "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 corroborates with the views presented at the regular meeting of the Nankai Trough Earthquake Assessment Committee on March 6 (reference below).)

(Reference)

Recent Crustal Activity Around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, March 6, 2026)
"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)."

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