Buldir Is M4.0 | Alaska Earthquake Center

Tectonic Setting of the Aleutian Islands

The Aleutian Arc marks the region where the Pacific Plate subducts under the North American Plate. It is an earthquake hotspot, as evidenced by the thousands of earthquakes that occur each year. Since 1900, the region has hosted several major megathrust earthquakes, including the 1957 M8.6 in the Andreanof Islands, the 1965 M8.7 in the Rat Islands, the 1986 M7.9 and the 1996 M7 .9 in the Andreanof Islands, and in 2003 M7.8 in the Rat Islands. Together they broke the entire length of the megathrust boundary in this area. Another notable source of earthquakes in the arc is a 6–9 mile (10–15 km) wide zone of deep central earthquakes within the Pacific Plate, known as the Wadati–Benioff Zone. The largest recorded deep earthquake centered in this area was the 2014 M7.9 Little Sitkin event. A third source of earthquakes in this area is shallow earthquakes related to volcanic processes and major faults within the North American Plate. They occur frequently and may produce a strong streak or streak.