Location:

Period:

8 Nov 2025 20:29:18 - 10 Nov 2025 09:58:59 (1 day 13 hours 29 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.4; 100 km ENE of Miyako, Japan; (20 Apr 2026) (52km from the swarm center)

15 swarms found nearby.

2011

PS20110311.6(159.4km)

11 Mar

2 days 8 hours

50 earthquakes

PS20110311.1(139.0km)

11 Mar

1 day 14 hours

28 earthquakes

PS20110311.7(24.8km)

11 Mar

3 days 15 hours

38 earthquakes

PS20110311.8(145.2km)

11 Mar

9 hours

5 earthquakes

PS20110315.1(60.0km)

14 Mar

1 day 10 hours

6 earthquakes

PS20110319.2(107.7km)

18 Mar

1 day 17 hours

8 earthquakes

PS20110323.1(42.9km)

22 Mar

23 hours

6 earthquakes

PS20110413.1(41.7km)

13 Apr

8 hours

6 earthquakes

PS20110916.1(62.1km)

16 Sep

1 day 11 hours

10 earthquakes

2012

PS20120314.1(193.9km)

14 Mar

2 hours

6 earthquakes

PS20120520.1(5.7km)

19 May

1 day 3 hours

9 earthquakes

2015

PS20150611.1(5.4km)

10 Jun

20 hours

5 earthquakes

2016

PS20160820.1(110.6km)

20 Aug

1 day 7 hours

6 earthquakes

2025

PS20251208.1(186.8km)

8 Dec

18 hours

9 earthquakes

2026

PS20260420.1(24.9km)

20 Apr

21 hours

9 earthquakes

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

Seismic Swarm PS20251108.1: Analysis of Activity East of Yamada, Japan

A seismic swarm designated PS20251108.1 occurred approximately 111 km east of Yamada, Japan, in the Pacific Ocean. The sequence began at 20:29 on 8 November 2025 and concluded at 09:58 on 10 November 2025, spanning 37 hours and 29 minutes. During this period, 25 earthquakes were recorded, with magnitudes ranging from 4.7 to 6.8 and focal depths primarily between 9 and 30 km.

The swarm featured several notable events. The initial shock reached magnitude 5.2 at 30 km depth. Subsequent activity included a magnitude 5.4 event at 12 km depth shortly afterward, followed by a magnitude 5.6 shock at 16 km. A cluster of stronger tremors occurred on 9 November, highlighted by a magnitude 6.8 earthquake at 18 km depth, accompanied by multiple events of magnitude 5.0 to 6.4 clustered at shallower depths around 10 km. Later activity tapered with events such as a magnitude 6.0 at 11 km depth on 10 November before the sequence ended.

This swarm unfolded within the tectonically active Japan Trench subduction zone, where the Pacific Plate converges with the overriding plate at rates of approximately 8–9 cm per year. The region experiences frequent seismicity due to plate boundary interactions, including megathrust earthquakes and associated aftershock sequences. Depths recorded in the swarm align with typical crustal and upper-mantle activity in this offshore setting.

Historical data indicate 13 prior swarms in the area since 2000. These occurred in 2011 (nine events), 2012 (two events), 2015 (one event), and 2016 (one event). Such episodic clusters reflect ongoing stress accumulation and release along the subduction interface. A magnitude 7.4 earthquake struck 100 km ENE of Miyako on 20 April 2026, located 52 km from the swarm center, underscoring the potential for larger events in proximity to these sequences.

Geological monitoring in this part of the Tohoku region benefits from dense seismic networks that track both isolated events and swarm patterns. The provided swarm parameters represent internal classifications from SeismoSight and illustrate typical characteristics of subduction-related activity without implying immediate precursors to larger quakes.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Japan Meteorological Agency (JMA) seismic reports (jma.go.jp)
National Oceanic and Atmospheric Administration (NOAA) tectonic summaries for the Japan Trench region