[5] The large megathrust earthquake had a moment magnitude (Mw) of 8.2 according to the United States Geological Survey (USGS).

[6] A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled.

In Perryville, the closest populated area to the quake, cracks appeared in drywalls and on the ground.

[12] The limited impact from this earthquake was attributed to it occurring offshore from the sparsely-populated Alaska Peninsula.

[21] It was felt with a maximum Modified Mercalli intensity of VI (Strong), causing limited damage in the relatively unpopulated region of the Alaska Peninsula.

While the earthquake generated an ocean-wide tsunami, the maximum wave height was only measured at 0.3 meters.

[22] An unusually weak tsunami was generated because the earthquake occurred at a deep depth of 35 km.

[23] In July 2020, the Aleutian Subduction Zone was the source of an Mw  7.8 earthquake which struck the same region south of the Alaska Peninsula.

[28] Previously, it was thought that the subducting plate in the Shumagin Gap was poorly coupled to the overriding crust, quietly slipping and preventing large quakes.

[34][35] This earthquake occurred along a north northwest striking strike-slip fault rather than the thrust mechanism seen in the July event.

[45] Adding that the earthquake with its strike-slip mechanism "made no sense" because of the location near a subduction zone.

The preliminary focal mechanism solution indicates rupture occurred on a fault dipping either shallowly to the northwest, or steeply to the southeast.

The location, mechanism and depth – and the large size of the event – are all consistent with slip occurring on the subduction zone interface between the two plates.

At the location of this event, the Pacific plate converges with North America to the northwest at a rate of about 64 mm/yr, subducting at the Alaska-Aleutians trench ~125 km to the southeast of the earthquake.

On March 4, 2021, nearly 5 months before the Alaska mainshock, an 8.1 magnitude earthquake struck the Kermadec Islands,[51] a sparsely populated territory owned by New Zealand, and another equally sized event struck the Sub-Antarctic British territory of the South Sandwich Islands on August 12 of that year.

[56] In Port San Luis (Avila Beach) on the Central Coast of California, a 1.3-foot (40 cm) tsunami surge was measured by the National Weather Service in a tweet.