At 5:36 in the evening on March 27, 1964, the ground under Prince William Sound started shaking and didn't stop for roughly four to five minutes, an almost unbelievable duration for an earthquake, long enough that people who lived through it still describe losing their balance repeatedly just trying to get outside.
The Second-Strongest Earthquake Ever Recorded
The 1964 Good Friday earthquake is now generally measured at magnitude 9.2, making it the second-strongest earthquake ever recorded worldwide, behind only the 1960 earthquake off the coast of Chile. That 9.2 figure is a modern refinement; the U.S. Geological Survey's original 1964 assessment placed it somewhat lower, in the 8.3 to 8.4 range, before later seismological methods revised the estimate upward. Both figures show up in different sources, which is worth knowing if the number you find doesn't match one you saw elsewhere.
The quake's epicenter sat in Prince William Sound, close enough to Seward, the small port town that serves as the main gateway to Kenai Fjords National Park, that the town felt the full force of both the shaking itself and what came immediately after.
Plan Your Kenai Fjords Visit
Seward is your starting point for the park. Most boat tours and the Exit Glacier trailhead both begin here.
Open the Trip PlannerSubsidence, Fire, and a Tsunami All at Once
Parts of the Seward waterfront subsided, sinking several feet as the ground itself settled after the shaking stopped, a permanent change to the town's elevation and shoreline that's still visible in how the area was rebuilt. Underwater landslides triggered local tsunami waves that struck Seward's harbor within minutes, and ruptured fuel tanks near the waterfront caught fire, adding burning oil on the water to a night that already included earthquake damage and flooding.
Statewide, the earthquake and the tsunamis it triggered killed well over a hundred people and caused deep, lasting damage across Southcentral Alaska, from Anchorage to the small coastal communities along the Gulf of Alaska. Seward rebuilt its harbor and waterfront in the decades since, but the geology underneath the town, and much of the coastline visitors now see from a Kenai Fjords tour boat, still carries the mark of that one five-minute stretch in 1964.
- Date MARCH 27, 1964
- Magnitude (modern estimate) 9.2
- Magnitude (original 1964 USGS estimate) 8.3–8.4
- Shaking duration ~4–5 MINUTES
Earthquake magnitude, duration, and date checked against U.S. Geological Survey historical earthquake records. Where the modern magnitude estimate (9.2) differs from the USGS's original 1964 assessment (8.3–8.4), both are given above rather than only the current figure, since the discrepancy is itself part of the historical record. Damage and casualty information at Seward checked against USGS and National Park Service historical materials on the Good Friday earthquake.
Board a tour boat out of Seward today and the town looks settled, its harbor busy with charter boats and cruise passengers rather than any visible trace of 1964. But the ground it's built on moved that night in ways that don't undo themselves, and the second-strongest earthquake ever measured is the reason the gateway to Kenai Fjords sits exactly where, and exactly how, it does now.