Location:

Period:

14 Mar 2011 23:22:02 - 16 Mar 2011 10:16:12 (1 day 10 hours 54 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.4; 100 km ENE of Miyako, Japan; (20 Apr 2026) (37km from the swarm center)

14 swarms found nearby.

2011

PS20110311.1(176.2km)

11 Mar

1 day 14 hours

28 earthquakes

PS20110311.7(53.3km)

11 Mar

3 days 15 hours

38 earthquakes

PS20110311.8(199.8km)

11 Mar

9 hours

5 earthquakes

PS20110319.2(144.6km)

18 Mar

1 day 17 hours

8 earthquakes

PS20110323.1(75.6km)

22 Mar

23 hours

6 earthquakes

PS20110413.1(55.0km)

13 Apr

8 hours

6 earthquakes

PS20110916.1(35.9km)

16 Sep

1 day 11 hours

10 earthquakes

2012

PS20120314.1(145.7km)

14 Mar

2 hours

6 earthquakes

PS20120520.1(56.4km)

19 May

1 day 3 hours

9 earthquakes

2015

PS20150611.1(55.5km)

10 Jun

20 hours

5 earthquakes

2016

PS20160820.1(51.7km)

20 Aug

1 day 7 hours

6 earthquakes

2025

PS20251108.1(60.0km)

8 Nov

1 day 13 hours

25 earthquakes

PS20251208.1(137.6km)

8 Dec

18 hours

9 earthquakes

2026

PS20260420.1(38.2km)

20 Apr

21 hours

9 earthquakes

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

Seismic Swarm PS20110315.1 Off the Coast of Miyako, Japan

Seismic swarm PS20110315.1 occurred approximately 169 km east-northeast of Miyako, Japan, within the tectonically active Japan Trench subduction zone. This region lies where the Pacific Plate subducts beneath the Okhotsk Plate at a rate of about 8–9 cm per year, generating frequent earthquakes and occasional large-magnitude events along the plate interface and within the overriding plate.

The swarm began at 23:22 UTC on 14 March 2011 and concluded at 10:16 UTC on 16 March 2011, spanning 34 hours and 54 minutes. During this interval, six earthquakes were recorded with the following parameters: a magnitude 5.2 event at 35 km depth on 14 March at 23:22, a magnitude 5.4 event at 12 km depth on 15 March at 08:01, a magnitude 5.5 event at 35 km depth on 15 March at 11:46, a magnitude 6.1 event at 18 km depth on 15 March at 15:23, a magnitude 4.1 event at 35 km depth on 15 March at 18:02, and a magnitude 5.2 event at 24 km depth on 16 March at 10:16. Depths ranged from 12 to 35 km, consistent with activity in both the shallow crust and the subducting slab.

This swarm represents one of three documented swarm sequences in the area since 2000, marking the earliest such episode in the instrumental record for the locale. The timing, shortly after the magnitude 9.0 Tohoku earthquake of 11 March 2011, aligns with the elevated aftershock productivity typical of the outer-rise and fore-arc domains in this subduction setting. Such swarms often reflect stress redistribution following major megathrust ruptures, with events clustered both spatially and temporally.

Geologically, the Miyako offshore area features a steep trench slope and accretionary prism, with crustal heterogeneity that can localize swarm activity along pre-existing faults. Historical seismicity in the broader Tohoku region demonstrates a recurrence of great earthquakes every few centuries, underscoring the persistent seismic hazard.

References

USGS Earthquake Catalog
Japan Meteorological Agency Seismic Database
Global CMT Catalog