Alaska Volcano Observatory

Beginning in early 2020, earthquake activity increased at Great Sitkin Volcano. On February 26, AVO elevated the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY, stating that earthquake activity was above background levels, and there had been no evidence of eruptive activity in geophysical data streams or in satelilte observations. A relatively large magnitude 3.5 earthquake occurred at Great Sitkin on March 6. It was located approximately 1 km east-southeast of the summit at shallow depths (not more than 2 km below sea level). After the quake, seismic activity returned to lower levels, and no eruptive activity has been detected in infrasound or satellite data. Another relatively large, M 5.3 earthquake occurred at 8:59:55.004 UTC, July 15, 2020 about 55 miles (90 km) west-northwest of Great Sitkin volcano. The earthquake was about 5 miles (8.5 km) deep and registered clearly on AVO seismic networks in the region including those on Great Sitkin, Kanaga, and Tanaga volcanoes. The earthquake does not appear to be related to volcanic activity and is most likely tectonic in origin.
Seismicity declined through the late summer and fall, and on October 21, 2020, AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL.