Alaska Earthquake of 1964

On March 27, 1964, at 5:36 p.m., the ground in Alaska began to shake and did not stop for four minutes. The Good Friday earthquake registered a 9.2 on the Richter scale, making it the second-largest earthquake ever recorded, behind only Chile’s 9.5 in 1960. It was a megathrust earthquake, the most destructive kind known, and it fundamentally changed both the coastline of Alaska and the science of seismology itself.

The Mechanics of a Megathrust

The 1964 earthquake was a megathrust event, the type responsible for all ten of the largest earthquakes ever recorded. It occurs at a subduction zone, where one tectonic plate slides beneath another. In this case, the Pacific Plate was diving under the North American Plate at the Alaska-Aleutian Subduction Zone. The problem is that the descending plate does not always slide smoothly. It can lock against the upper plate, building immense pressure over time. When that pressure finally releases, the entire region lurches forward suddenly. In 1964, an area roughly 500 miles long and 125 miles wide moved between 30 and 60 feet in seconds. The earthquake itself lasted for four minutes.

Destruction on Land and Sea