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Magnitude 4.8 - 28 miles S of Atka Pass
April 7, 2023 23:17:40 AKDT (April 8, 2023 07:17:40 UTC)
51.6170°N 175.2272°W Depth 27.8 miles (45 km)
This event has been reviewed by a seismologist
- 32 miles (51 km) S of Mt. Sergief
- 40 miles (64 km) S of Kasatochi Island
- 42 miles (68 km) S of Koniuji Island
- 49 miles (79 km) SE of Great Sitkin Island
- 59 miles (95 km) SW of Atka
- 63 miles (102 km) SE of Mt. Adagdak
- 64 miles (103 km) E of Adak
- 68 miles (110 km) E of Mt. Moffett
- 85 miles (137 km) E of Kanaga Volcano
- 97 miles (157 km) E of Bobrof Island
- 126 miles (204 km) E of Tanaga Volcano
- Magnitude type: Mb2
- Event type: earthquake
Tectonic Setting of the Aleutian Islands
The world's largest earthquakes originate along convergent plate boundaries such as the Aleutian megathrust. Starting in 1938, a series of three great earthquakes ruptured the subduction zone along its entire length from the Alaska Peninsula to the western Aleutians with the exception of a small gap near the Shumagin Islands. The sequence began with a M8.2 earthquake southwest of Kodiak Island. A M8.6 in the Andreanof Islands followed in 1957, and the sequence concluded with the Rat Islands M8.7 in 1965. The Shumagin Gap still has not ruptured, but GPS observations suggest that little strain has built up in this region.
Another notable source of seismicity in the arc are the intermediate depth earthquakes within the subducting Pacific Plate, known as the Wadati-Benioff zone. The largest recorded earthquake of this kind was the 2014 M7.9 Little Sitkin event. Shallow earthquakes associated with volcano processes and crustal faults within the overriding North American plate occur regularly and may produce vigorous aftershock or swarm-like sequences.