October 2020 Alaska Peninsula earthquake

This earthquake occurred along a north northwest striking strike-slip fault rather than the thrust mechanism seen in the July event.[5][6] It did not occur along the megathrust boundary but within one of the two interacting plates. Maximum slip along the fault is estimated at 3.4 meters.[5]

As for the July 22 thrust earthquake, that event occurred on the Shumagin Gap; an area on the Aleutian Megathrust which has not slipped for decades.[7] That section of the megathrust was previously thought to experience slow creep as no earthquakes have been seen on the gap for a century, while the recurrence interval for megathrust events there is 50 to 90 years. It is situated between the rupture zone of the 1946 and 1938 earthquake. This event appears to only unlock the deeper part of the fault, with the shallow portion still capable of generating a large tsunami.[8] In addition, the slip generated by the earthquake is small for its size, with the potential for large earthquakes again in the future.[9]

A tsunami warning was issued but was later downgraded to an advisory.[10] A wave was measured at 2.3 ft. (70.1 cm) at Sand Point.[11] At King Cove, the tsunami had a wave height of 2.1 ft. (64.0 cm) and was 2.5 ft. at Chignik Bay.[12][13] As of 7:05 pm (AKDT), the tsunami alert is at Advisory level. In the state of Hawaii, alert level Advisory was issued at 5:55 pm.[14] Wave heights ranging between 0.1-1.2 ft (2–38 cm) were detected along the islands.[15] Tsunami warning was later cancelled at 05:05:15 (UTC).[16]

As of 2020-10-26, there has been 167 recorded aftershocks, including nine that registered greater than M_w 5.0. The largest was an M_w 5.9 on October 19.[17] Other large aftershocks include an M_w 5.8, 5.7, 5.6 and 5.5.[18][19][20][21]