Location:

Period:

5 Jan 2008 10:39:14 - 6 Jan 2008 00:20:32 (13 hours 41 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

6 swarms found nearby.

2008

PS20080828.1(175.4km)

27 Aug

5 hours

5 earthquakes

2012

PS20121028.1(98.5km)

28 Oct

1 day 8 hours

23 earthquakes

PS20121030.1(115.0km)

30 Oct

11 hours

5 earthquakes

2013

PS20130904.1(64.7km)

3 Sep

4 hours

5 earthquakes

2019

PS20191223.1(149.4km)

23 Dec

6 hours

5 earthquakes

2023

S20230914.1(99.6km)

13 Sep

4 days 21 hours

74 earthquakes

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Seismic Swarm PS20080105.1: January 2008 Events off British Columbia

A seismic swarm designated PS20080105.1 occurred 298 km west-northwest of Port McNeill, Canada, beginning at 10:39 UTC on 5 January 2008 and concluding at 00:20 UTC on 6 January 2008. Over 13 hours and 41 minutes, six earthquakes were recorded in this offshore region of the northeastern Pacific Ocean.

The sequence initiated with a magnitude 5.7 event at 10 km depth. Roughly 22 minutes later, a magnitude 6.6 earthquake struck at 15 km depth, marking the largest event. Subsequent shocks included a magnitude 6.4 at 10 km depth, followed by two magnitude 5.0 events—one at 10 km and another at 60 km depth. The swarm ended with a magnitude 5.4 event at 10 km depth. Most activity clustered at shallow crustal depths, consistent with tectonic release along plate boundaries.

This location lies within the tectonically active zone influenced by the Explorer Plate, which interacts with the Pacific Plate to the west and the North American Plate to the east. The area features a combination of divergent spreading centers and transform faults that accommodate relative plate motions. Seismic swarms here often reflect episodic strain release rather than mainshock-aftershock sequences, driven by fluid migration or aseismic slip along fault networks.

Geologically, the broader region forms part of the northern extension of the Cascadia subduction system, though the specific swarm site aligns more closely with the Explorer Ridge and associated fracture zones. Historical records document recurrent moderate-to-large earthquakes in this offshore domain, with notable activity clusters in the late 20th and early 21st centuries linked to plate boundary adjustments. Ongoing monitoring by regional seismic networks continues to track such events for improved hazard assessment.

The January 2008 swarm highlights the dynamic nature of this plate margin, where shallow seismicity predominates due to the relatively thin oceanic crust. Depths ranging from 10 to 60 km indicate both crustal and possible upper-mantle involvement in the deeper event.

References

SeismoSight internal swarm classification PS20080105.1
Geological Survey of Canada tectonic summaries for the Explorer Plate region
USGS Earthquake Catalog historical data for northeastern Pacific offshore events