The 1957 Andreanof Islands earthquake occurred at 04:22 local time on March 9 with a moment magnitude estimated at 8.6 and a maximum Modified Mercalli intensity of VIII (Severe).

A basin-wide tsunami followed, with effects felt in Alaska and Hawaii, and strong waves recorded across the Pacific rim.

[5] At each terminus of the subduction zone, convergence ends in favor of right-lateral transform faults.

[9] In the west, convergence becomes increasingly oblique until the Commander Islands where faulting is nearly completely strike-slip—a 2017 earthquake was associated with this tectonic setting.

[2] As the shock occurred before the World Wide Standardised Seismological Network was in operation, few instruments recorded the event, and its mechanism is not understood well as a result.

Some effort was made with the limited data to gain an understanding of the rupture area and the distribution of slip.

One aspect of the event that was certain was that the 1,200–1,230 km (750–760 mi) aftershock zone was one of the largest that had ever been observed,[12][13] comparable to the approximate lower rupture length limit of the 2004 Indian Ocean earthquake.

[20] If the eastern portion of the megathrust did rupture, then a magnitude of Mw 9.0–9.1 is more reflective of the event.

[7] Also on Unimak, near the Scotch Cap Lighthouse that was destroyed in the 1946 earthquake, run up heights of 12–15 m (39–49 ft) were observed.

[14] At Yakutat run-ups measured 0.3 m (1 ft 0 in), while Women's Bay, Kodiak, Seward, and Juneau had recorded tsunami heights of 0.2 m (7.9 in).

[14] At Fagasā, American Samoa, tsunami run-up heights reached 1.5 m (4 ft 11 in).

[14] In Mexico, the tidal gauge in Ensenada, Baja California recorded the strongest waves at 1.0 m (3.4 ft).

[22] Valparaíso, Chile recorded wave heights of 2.0 m (6.7 ft), which were the highest across the country.

[14] The earthquake caused severe damage to roads and buildings on Adak including a crack 4.5 m (15 ft) in size,[6] however there were no deaths.

[14] At Chernofski,[25] Trappers Cove, and Vsevidof, strong waves drowned sheep.

[14] In Hawaii, damage was much more extensive, including two indirect fatalities that occurred when a pilot and photographer were killed while attempting to document the tsunami's arrival from an airplane.

About 50 homes were flooded on the north shore of Oahu and significant effects were seen in Waialua Bay.