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Magnitude 3.0 - 131 miles S of Bobrof Island
May 20, 2023 21:22:26 AKDT (May 21, 2023 05:22:26 UTC)
50.0064°N 177.4024°W Depth 15.6 miles (25 km)
This event has been reviewed by a seismologist
- 133 miles (215 km) S of Adak
- 133 miles (215 km) S of Kanaga Volcano
- 134 miles (217 km) S of Tanaga Volcano
- 136 miles (220 km) S of Mt. Moffett
- 137 miles (222 km) SE of Mt. Gareloi
- 141 miles (228 km) S of Mt. Adagdak
- 152 miles (246 km) S of Great Sitkin Island
- 164 miles (265 km) SW of Atka Pass
- 170 miles (275 km) SW of Kasatochi Island
- 177 miles (286 km) SW of Mt. Sergief
- 182 miles (295 km) SW of Koniuji Island
- Magnitude type: Ml2
- 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.