Seismic Swarm S20221111.1 Near Shungnak, Alaska
An earthquake swarm designated S20221111.1 occurred 62 km south of Shungnak in northwest Alaska. The sequence began at 08:29 on 10 November 2022 and concluded at 13:44 on 13 November 2022, spanning 77 hours and 15 minutes. During this period, 48 earthquakes were recorded.
The events exhibited magnitudes predominantly between 1.0 and 2.9, with the largest reaching 2.9 at a depth of 9 km on 12 November. Depths ranged from near-surface (0 km) to 33 km, indicating activity within the upper crust. The temporal distribution showed peak activity on 10 November, with 18 events, followed by 19 on 11 November, 7 on 12 November, and 4 on 13 November.
Northwest Alaska lies within the Arctic Alaska tectonic province, characterized by Paleozoic to Mesozoic sedimentary and metamorphic rocks of the Brooks Range fold-and-thrust belt. Seismicity in this region arises from intraplate deformation linked to far-field stresses from the Pacific Plate subduction zone to the south, as well as local fault systems such as the Kobuk and Tintina fault zones. Historical records indicate moderate background seismicity, with swarms representing episodic clusters often associated with fluid migration or minor fault reactivation rather than large mainshock-aftershock sequences.
Since 1 January 2000, seven such swarms have been documented in the area. Earlier episodes occurred in 2019 (six events) and 2020 (one event), suggesting recurrent but infrequent swarm behavior in this sector of the Brooks Range margin.
The November 2022 swarm aligns with this pattern of low-to-moderate magnitude activity. No damage or felt reports were associated with the events, consistent with their modest magnitudes and remote location. Continued monitoring by regional seismic networks remains essential for understanding long-term strain accumulation in this tectonically subtle portion of Alaska.
References
- Alaska Earthquake Center, University of Alaska Fairbanks (updated 2023 seismic catalog).
- USGS Earthquake Hazards Program regional tectonics summary for northern Alaska.
- SeismoSight internal swarm classification database.