Location:

Period:

23 Sep 2014 14:08:08 - 26 Sep 2014 15:15:08 (3 days 1 hour 7 minutes)

Volcanoes in 100km radius:

None

Earthquakes:

3 swarms found nearby.

2008

S20080925.1(18.9km)

24 Sep

3 days 6 hours

43 earthquakes

2015

S20151006.1(22.5km)

5 Oct

1 day 12 hours

30 earthquakes

2019

S20191109.1(10.4km)

8 Nov

5 days 13 hours

59 earthquakes

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Seismic Swarm S20140924.1: Analysis of Activity Northwest of Yakutat, Alaska

Seismic swarm S20140924.1 occurred approximately 115 km northwest of Yakutat, Alaska, between 14:08 on 23 September 2014 and 15:15 on 26 September 2014. Over 73 hours and 7 minutes, the event sequence registered 42 earthquakes, all of low magnitude. This activity provides a window into the persistent tectonic deformation along the northern Pacific margin.

The Yakutat region lies at the tectonic boundary where the Yakutat terrane collides with the North American plate. This collision drives the St. Elias orogeny, producing rapid uplift in the Chugach-St. Elias Mountains and elevated seismicity. The Pacific plate subducts northwestward beneath the margin at rates of approximately 5–6 cm per year, while the buoyant Yakutat block resists subduction and induces shallow crustal faulting. Historical records document recurrent moderate-to-large earthquakes in this zone, reflecting both megathrust and intraplate mechanisms.

Magnitudes within the swarm ranged from 0.7 to 1.4, with the majority clustered between 0.9 and 1.3. Depths were predominantly near-surface, although two events reached 6 km and 8 km. The temporal distribution showed highest frequency during the first 24 hours, followed by a gradual decline. Such patterns are characteristic of swarm sequences driven by fluid migration or slow slip rather than a single mainshock-aftershock cascade.

Since 1 January 2000, only one prior swarm has been documented in the immediate area, occurring in 2008. This low recurrence rate underscores the episodic nature of clustered microseismicity in the region despite continuous tectonic loading.

The 2014 swarm did not produce felt shaking or damage, consistent with its maximum magnitude of 1.4. Monitoring by regional networks continues to refine understanding of strain accumulation along the plate interface, supporting long-term hazard assessment for coastal Alaska communities.

References

USGS Earthquake Catalog (earthquake.usgs.gov)
Alaska Earthquake Center (aeic.alaska.edu)
Geological Society of America, St. Elias orogeny syntheses