Location:

Period:

22 Mar 2011 22:12:31 - 23 Mar 2011 10:43:36 (12 hours 31 minutes)

Volcanoes in 100km radius:

Nasudake(98km)

Earthquakes:

M 7.0+:

M 7.9; 47 km E of ?arai, Japan; (11 Mar 2011) (65km from the swarm center)

23 swarms found nearby.

2008

PS20080507.1(103.1km)

7 May

17 hours

11 earthquakes

PS20081220.1(113.4km)

20 Dec

22 hours

6 earthquakes

2011

PS20110309.1(147.2km)

9 Mar

7 days 12 hours

159 earthquakes

PS20110311.2(160.8km)

11 Mar

21 hours

21 earthquakes

PS20110311.4(109.3km)

11 Mar

8 hours

57 earthquakes

PS20110311.3(141.4km)

11 Mar

1 day 17 hours

44 earthquakes

PS20110311.5(99.1km)

11 Mar

7 hours

10 earthquakes

PS20110312.2(60.0km)

11 Mar

20 hours

6 earthquakes

PS20110312.1(195.1km)

11 Mar

1 day 3 hours

8 earthquakes

PS20110313.1(133.3km)

13 Mar

3 days 13 hours

14 earthquakes

PS20110314.1(23.1km)

13 Mar

13 hours

14 earthquakes

PS20110317.1(102.1km)

16 Mar

1 day 16 hours

10 earthquakes

PS20110319.1(31.0km)

18 Mar

1 day 7 hours

6 earthquakes

PS20110320.1(91.4km)

20 Mar

1 day 4 hours

6 earthquakes

PS20110322.1(106.4km)

22 Mar

2 days 5 hours

14 earthquakes

PS20110411.1(61.6km)

10 Apr

1 day 7 hours

7 earthquakes

S20110411.2(54.8km)

11 Apr

1 day 16 hours

35 earthquakes

2014

PS20140711.1(127.3km)

11 Jul

13 minutes

5 earthquakes

2016

PS20161121.1(53.7km)

21 Nov

20 hours

11 earthquakes

S20161122.1(63.3km)

21 Nov

2 days 0 hours

42 earthquakes

2021

S20210214.1(99.2km)

13 Feb

3 days 9 hours

49 earthquakes

PS20210804.1(118.4km)

3 Aug

18 hours

5 earthquakes

2022

PS20220316.1(127.8km)

16 Mar

1 hours

7 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm PS20110322.3: Post-Tohoku Seismicity Near Ishikawa, Japan

A seismic swarm designated PS20110322.3 was recorded in the region 12 km east-southeast of Ishikawa, Japan. The sequence began at 22:12 on 22 March 2011 and concluded at 10:43 on 23 March 2011, spanning 12 hours and 31 minutes. During this interval, six earthquakes were registered, with magnitudes ranging from 5.0 to 5.5 and focal depths between 16 km and 40 km.

The events unfolded rapidly after the initial pair of magnitude-5.5 shocks at 22:12:31 (18 km depth) and 22:13:57 (40 km depth). Subsequent activity included a magnitude-5.5 event at 22:35:00 (37 km depth), a magnitude-5.2 shock at 22:36:32 (16 km depth), a magnitude-5.0 earthquake at 22:53:31 (34 km depth), and a final magnitude-5.1 event at 10:43:36 on 23 March (35 km depth). These closely spaced occurrences reflect typical swarm behavior, characterized by multiple events of similar magnitude without a single dominant mainshock.

Japan lies within the Pacific Ring of Fire, where complex interactions among the Pacific, Philippine Sea, and Eurasian plates drive frequent seismicity. The Ishikawa area sits near the western margin of Honshu, influenced by both regional fault systems and distant stress changes from major subduction-zone ruptures. The swarm occurred eleven days after the magnitude-7.9 earthquake of 11 March 2011, located 47 km east of Ibaraki and approximately 65 km from the swarm centroid. This proximity suggests the sequence may represent triggered aftershock activity or secondary fault responses within the broader aftershock zone.

Historical records since 1 January 2000 indicate 15 swarms in the vicinity. Earlier episodes include two swarms in 2008 and thirteen in 2011, underscoring elevated seismic clustering during periods of heightened regional strain. Such patterns align with Japan's tectonic setting, where subduction-related loading periodically activates distributed fault networks.

References

Japan Meteorological Agency seismic catalogs (2011)
United States Geological Survey Earthquake Hazards Program
SeismoSight internal swarm classification database