This evening’s M7.8 earthquake [7/21/20, 10:12 PM AKDT] occurred on the well-known subduction zone interface off the Alaska Peninsula. Strong shaking has been reported from Perryville and Sand Point to King Cove and Cold Bay.
We use the phrase “magnitude of completeness” often when referring to our understanding of seismicity in a region or following a sequence of earthquakes. This value is a simplistic assessment of a catalog of earthquakes.
We are getting questions about current earthquake activity in the western Aleutians—and with good reason. There are actually two different sequences of earthquakes unfolding right now in the Andreanof and Rat Islands.
Seismicity in Alaska had another stand-out year in 2019. With a total of 50,289 reported earthquakes, 2019 finished as a runner up to the record-breaking 2018 (figure 1). The earthquake depths ranged between 0 and 165 miles (265 km).