Location:

Magnitude:

7.1

Time:

13 Feb 2021 14:07:49

Depth:

43.9

M 7.0+:

M 7.3; 57 km ENE of Namie, Japan; (16 Mar 2022) (17km from the earthquake)
M 7.0; 30 km E of Ishinomaki, Japan; (20 Mar 2021) (81km from the earthquake)
M 7.1; 29 km ESE of Ishinomaki, Japan; (7 Apr 2011) (63km from the earthquake)
M 9.1; 2011 Great Tohoku Earthquake, Japan; (11 Mar 2011) (82km from the earthquake)
M 7.0; 107 km E of Namie, Japan; (19 Jul 2008) (43km from the earthquake)
M 7.2; 66 km ESE of Ishinomaki, Japan; (16 Aug 2005) (65km from the earthquake)
M 7.0; 133 km ESE of Ishinomaki, Japan; (31 Oct 2003) (74km from the earthquake)

There are 8 swarms found nearby.

2011

PS20110309.1(43.7km)

9 Mar

7 days 12 hours

159 earthquakes

PS20110311.3(25.5km)

11 Mar

1 day 17 hours

44 earthquakes

PS20110312.2(85.0km)

11 Mar

20 hours

6 earthquakes

PS20110311.8(99.0km)

11 Mar

9 hours

5 earthquakes

2016

PS20161121.1(65.2km)

21 Nov

20 hours

11 earthquakes

S20161122.1(53.8km)

21 Nov

2 days 0 hours

42 earthquakes

2021

S20210214.1(17.5km)

13 Feb

3 days 9 hours

49 earthquakes

2022

PS20220316.1(11.8km)

16 Mar

1 hours

7 earthquakes

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Seismic Activity in Japan's Tohoku Region: The February 2021 M7.1 Earthquake

On February 13, 2021, at 14:07 local time, a magnitude 7.1 earthquake struck 73 km east-northeast of Namie, Japan, at a depth of 43.9 km. This event occurred within the tectonically active Japan Trench subduction zone, where the Pacific Plate converges with the Okhotsk Plate at rates exceeding 8 cm per year. The hypocentral parameters place the rupture in the outer-rise or upper-plate region east of the Fukushima and Miyagi prefectures, consistent with the region's history of intraslab and interface seismicity.

The Tohoku region has experienced recurrent large-magnitude earthquakes due to its position along the convergent margin. Subduction-related megathrust events, intraslab earthquakes within the descending Pacific slab, and shallow crustal events all contribute to the seismic hazard. The February 2021 shock fits the pattern of moderate-to-large events that frequently follow or precede major ruptures along the trench.

Strong earthquakes since 2000 in the vicinity include the following, with distances measured from the February 2021 epicenter: an M7.3 event 57 km ENE of Namie on 16 March 2022 (17 km distant); an M7.0 event 30 km east of Ishinomaki on 20 March 2021 (81 km distant); the M7.1 event of 13 February 2021 itself; an M7.1 event 29 km ESE of Ishinomaki on 7 April 2011 (63 km distant); the M9.1 Great Tohoku Earthquake on 11 March 2011 (82 km distant); an M7.0 event 107 km east of Namie on 19 July 2008 (43 km distant); an M7.2 event 66 km ESE of Ishinomaki on 16 August 2005 (65 km distant); and an M7.0 event 133 km ESE of Ishinomaki on 31 October 2003 (74 km distant). These events illustrate persistent seismic productivity along the margin, with several occurring within tens of kilometers of one another.

The 2011 M9.1 Tohoku earthquake remains the dominant recent event, having produced widespread strong ground motion, a devastating tsunami, and long-term afterslip and viscoelastic relaxation that continue to modulate regional stress. Subsequent activity, including the 2021 and 2022 events, occurs in areas of post-seismic readjustment. Depths around 40–50 km for several of these shocks align with the expected range for intraslab seismicity within the subducting Pacific Plate.

Continued monitoring by regional and global seismic networks is essential for characterizing ongoing strain accumulation and release along the Japan Trench. The spatial clustering of M7+ events near Namie and Ishinomaki underscores the need for resilient infrastructure and updated probabilistic seismic hazard assessments in northeastern Honshu.

References USGS Earthquake Catalog (event parameters and locations as provided)