Major Earthquakes in Alaska

Alaska's Earthquake History

The earth's most active seismic feature, the circum-Pacific seismic belt, brushes Alaska and the Aleutian Islands, where more earthquakes occur than in the other 49 States combined. More than 80 percent of the planet's tremors occur in the circum-Pacific belt, and about six percent of the large, shallow earthquakes are in the Alaska area, where as many as 4,000 earthquakes at various depths are detected in a year.

The 1964 Good Friday Earthquake

On March 27, 1964, at 5:36 p.m. ADT a great earthquake of magnitude 9.2 occurred in Prince William Sound region of Alaska. The epicenter was about 10 km east of the mouth of College Fiord, approximately 90 km west of Valdez and 120 km east of Anchorage. The epicenter was located at Lat. 61.04N, Lon. 147.73W, at a depth of approximately 25 km. This earthquake is the second largest earthquake ever recorded in the world, after a M9.5 earthquake in Chile in 1960. The duration of rupture lasted approximately 4 minutes.

Notable Earthquakes in Alaska and Aleutians

Alaska has a long history of significant seismic events that have shaped the state's landscape, communities, and approach to preparedness. Some of the most notable include:

1957 Andreanof Islands — M9.1: Generated a major tsunami affecting the Hawaiian Islands.
1964 Good Friday Earthquake — M9.2: The largest earthquake in North American recorded history. Full details.
1965 Rat Islands — M8.7: One of the largest earthquakes ever recorded in the Aleutian chain.
2002 Denali Fault Earthquake — M7.9: The largest inland earthquake in North American history, rupturing 340 km of the Denali Fault.
2018 Anchorage Earthquake — M7.1: Caused significant infrastructure damage in Anchorage but no direct fatalities, partly due to improved building codes post-1964.

Alaska's earthquake catalog stretches back centuries through geological and historical records, indicating that major seismic events have repeatedly affected the state long before modern monitoring began.

Active Faults

Alaska contains numerous active fault systems that pose ongoing earthquake hazards. The principal seismic features include the Aleutian megathrust subduction zone, the Denali Fault system, the Castle Mountain Fault near Anchorage, and various fault networks in the Fairbanks area and Southeast Alaska.

Map of historic earthquake locations, active faults, and rupture zones in Alaska. Click for larger view.

Additional Resources

The following organizations provide authoritative information about Alaska's seismic activity:

West Coast/Alaska Tsunami Warning Center — Monitors the Pacific Ocean for tsunami-generating earthquakes and issues warnings for the US West Coast and Alaska.
USGS Earthquake Hazards Program — The federal program dedicated to monitoring earthquakes and volcanic activity nationwide and providing hazard assessments.
Alaska Earthquake Center (University of Alaska Fairbanks) — The primary earthquake monitoring agency for Alaska, operating the statewide seismic network.
Alaska Division of Geological & Geophysical Surveys (DGGS) — Maintains the Quaternary fault and fold database for Alaska, documenting active fault locations and hazard zones.

Multimedia Resources

Though the Earth Be Moved — Documentary chronicling the first 72 hours after the 1964 Alaska Earthquake.
Ocean Fury: Tsunamis in Alaska — A video by Alaska Sea Grant documenting tsunami hazards in Alaska.
Magnitude 9.2 — A 4-minute video by USGS geologist George Plafker relating how the largest quake in U.S. history had profound and lasting impacts. This video explains how the 1964 earthquake confirmed key aspects of plate tectonics theory.