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Location:
Gulf of Alaska
Period:
23 Jan 2018 10:09:00 - 25 Jan 2018 16:47:10 (2 days 6 hours 38 minutes)
Volcanoes in 100km radius:
None
Earthquakes:
50
2 swarms found nearby.
2018
PS20180123.1(51.3km)
23 Jan
1 day 12 hours
9 earthquakes
S20180124.2(24.3km)
23 Jan
2 days 1 hours
36 earthquakes
AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

Seismic Swarm S20180124.4: Analysis of the January 2018 Event in the Gulf of Alaska

Seismic swarm S20180124.4 occurred in the Gulf of Alaska, beginning at 10:09 on 23 January 2018 and concluding at 16:47 on 25 January 2018. Over this 54-hour and 38-minute period, 50 earthquakes were recorded. The swarm represents the sole seismic swarm documented in the region since 1 January 2000.

The events clustered tightly in both time and space, with magnitudes ranging from 3.0 to 4.5. Depths remained predominantly shallow, between 5 km and 20 km. Notable events included multiple magnitude 4.5 earthquakes on 23 January at depths of 17 km, 8 km, and 20 km, followed by a magnitude 4.3 event on 25 January at 8 km depth. The sequence exhibited no clear mainshock-aftershock pattern, consistent with swarm behavior driven by fluid migration or localized stress adjustments rather than a single large rupture.

The Gulf of Alaska lies within the tectonically active Pacific Ring of Fire, where the Pacific Plate subducts beneath the North American Plate along the Aleutian Trench. This convergent margin produces frequent seismicity, including megathrust earthquakes such as the 1964 Great Alaska Earthquake of magnitude 9.2. Historical records indicate persistent background activity, with smaller events commonly occurring due to ongoing plate convergence at rates of approximately 5–6 cm per year.

Swarm S20180124.4 aligns with the region's history of episodic clustered seismicity. Depths in this swarm correspond to the upper crustal levels where brittle failure is typical in subduction-related settings. The absence of additional swarms since 2000 underscores the relative rarity of such concentrated sequences in this portion of the margin.

This event provides insight into short-term seismic clustering mechanisms in subduction zones. The consistent shallow depths suggest activity within the overriding plate or near the plate interface, potentially influenced by pore-pressure changes. Continued monitoring remains essential for understanding how such swarms relate to broader tectonic loading in the Gulf of Alaska.

References

USGS Earthquake Catalog
Alaska Earthquake Center historical data
SeismoSight internal swarm classification records