Location:

Period:

30 Jul 2025 00:01:04 - 31 Jul 2025 07:21:40 (1 day 7 hours 20 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

M 7.0+:

M 7.5; 221 km SSE of Severo-Kuril’sk, Russia; (25 Mar 2020) (59km from the swarm center)

8 swarms found nearby.

2004

PS20041218.1(167.6km)

18 Dec

2 hours

7 earthquakes

2018

PS20181011.1(140.4km)

10 Oct

15 hours

9 earthquakes

2025

PS20250730.4(197.1km)

29 Jul

1 day 13 hours

45 earthquakes

PS20250729.1(142.0km)

29 Jul

2 days 20 hours

67 earthquakes

PS20250730.1(131.2km)

29 Jul

1 day 7 hours

16 earthquakes

PS20250803.1(111.8km)

2 Aug

1 day 2 hours

9 earthquakes

PS20250804.1(114.2km)

3 Aug

22 hours

5 earthquakes

2026

PS20260607.1(106.7km)

7 Jun

9 hours

5 earthquakes

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Seismic Swarm PS20250730.2: Analysis of Recent Activity East of Severo-Kuril’sk

A seismic swarm designated PS20250730.2 was recorded east of Severo-Kuril’sk, Russia, beginning at 00:01 on 30 July 2025 and concluding at 07:21 on 31 July 2025. The sequence, located 97 km east of Severo-Kuril’sk, comprised 15 earthquakes over 31 hours and 20 minutes. This event unfolded within the tectonically active Kuril Islands arc, a region shaped by ongoing subduction processes.

The swarm exhibited a range of magnitudes from 4.7 to 6.2, with focal depths varying between 10 km and 50 km. Notable events included a magnitude 5.9 quake at 37 km depth on 30 July at 02:30:40 UTC, followed by a magnitude 6.2 event at 15 km depth on 31 July at 05:27:14 UTC. Multiple magnitude 5+ shocks clustered in the initial hours, with several shallow events at 10 km depth later in the sequence. Such swarms typically reflect fluid migration or stress adjustments along fault networks rather than a single dominant rupture.

The Kuril Islands lie along the Kuril-Kamchatka subduction zone, where the Pacific Plate descends beneath the Okhotsk Plate at rates exceeding 8 cm per year. This setting produces frequent seismic activity, including both shallow crustal events and deeper intraslab earthquakes. The regional geology features volcanic arcs and trench systems that have generated significant historical seismicity, with the islands themselves formed through repeated magmatic and tectonic episodes over millions of years.

Since 2000, five swarms have been documented in the area, occurring in 2004 (one swarm), 2018 (one swarm), and 2025 (three swarms). A magnitude 7.5 earthquake struck 221 km south-southeast of Severo-Kuril’sk on 25 March 2020, approximately 59 km from the center of the current swarm, underscoring the persistent seismic hazard in this segment of the arc.

This latest swarm adds to the pattern of clustered activity observed in the region. Monitoring such sequences provides valuable data on stress transfer within the subduction interface, aiding assessments of potential larger events. Continued observation remains essential given the area's history of producing destructive earthquakes and associated tsunamis.

References

USGS Earthquake Catalog (regional subduction zone data)
Global CMT Project (focal mechanism context for Kuril arc)