Earthquake Seismic Activity Detected Near Iliamna Volcano in Southern Alaska
On December 5, 2023, at 00:56:11 AKST (09:56:11 UTC), a magnitude 2.7 earthquake occurred approximately 25 miles south of Iliamna Volcano. The event had a depth of 55.7 miles (90 km) and was located at 59.6979°N, 152.8526°W.
Tectonic Setting of Southern Alaska
Earthquakes in Southcentral Alaska result from various tectonic features:
- Megathrust Fault: The strongest earthquakes are generated by the megathrust fault, marking the contact zone between the subducting Pacific and overriding North American plates. The infamous 1964 M9.2 Great Alaska Earthquake originated under Prince William Sound.
- Wadati-Benioff Zone: Intermediate-depth seismicity (below 20 miles/32 km) occurs in this zone, where the subducting Pacific Plate descends towards the mantle beneath the North American Plate. It extends along the Aleutian Arc, Alaska Peninsula, Cook Inlet, and terminates beneath the northern foothills of the Alaska Range. Notable events include the 2016 M7.1 Iniskin and the 2018 M7.1 Anchorage earthquakes.
- Crustal Seismicity: Earthquakes in this category result from three main sources – the faults and folds of the Cook Inlet basin, the Castle Mountain Fault, and a broad zone of diffuse seismicity extending from northern Cook Inlet to the Denali Fault. Geological structures in upper Cook Inlet, including the Castle Mountain Fault, are capable of generating significant earthquakes.
The earthquake in the region and its complex tectonic setting underscores the potential for seismic activity, with historical earthquakes causing damage to structures and infrastructure. Monitoring and understanding these seismic events contribute to ongoing efforts to mitigate the impact of earthquakes in the region.
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