Earthquakes in Alaska — Historic Seismic Activity Map
Map of historic earthquake locations, active faults, and rupture zones in Alaska. Click for full-size view.
About This Map
This map illustrates the distribution of historic earthquake epicenters, known active faults, and the extents of major earthquake rupture zones across Alaska. The concentration of seismic activity visible on this map reflects Alaska's position at the junction of the Pacific and North American tectonic plates—one of the most geologically active boundaries on Earth.
The dense cluster of earthquake epicenters along the southern coast of Alaska and the Aleutian Island chain marks the subduction zone where the Pacific plate dives beneath North America. This boundary, known as the Aleutian megathrust, is responsible for Alaska's most powerful earthquakes, including the 1964 Good Friday Earthquake (magnitude 9.2), the 1957 Andreanof Islands earthquake (magnitude 9.1), and the 1965 Rat Islands earthquake (magnitude 8.7)—three of the ten largest earthquakes ever recorded by modern seismographs.
The Denali Fault, visible as a prominent linear feature extending across the interior of Alaska, is a major transform boundary capable of producing very large earthquakes. In 2002, the Denali Fault produced a magnitude 7.9 earthquake—the largest inland earthquake in North American recorded history—rupturing 340 kilometers of fault and generating ground displacements of up to 8 meters in some locations.
Understanding Alaska's Seismic Zones
Alaska's seismicity can be divided into several distinct zones based on tectonic setting and characteristic earthquake behavior:
- Aleutian Subduction Zone: The dominant seismic feature in Alaska, extending from the Alaska Peninsula southwest through the entire Aleutian chain. This zone generates the state's largest earthquakes (up to magnitude 9+) through periodic rupture of the plate boundary interface. Earthquakes in this zone also generate tsunamis that affect communities throughout the Pacific basin.
- Southcentral Alaska: The Gulf of Alaska and Prince William Sound region, including the Cook Inlet area and the vicinity of Anchorage, experience frequent moderate-to-large earthquakes from the subducting Pacific slab and associated faults in the overriding North American plate.
- Interior Alaska Fault Systems: The Denali Fault and associated structures in Alaska's interior produce large crustal earthquakes unrelated to subduction processes. These strike-slip faults generate surface rupture and can affect communities far from the coast.
- Yakutat Block: The Yakutat microplate, colliding with southern Alaska near Glacier Bay, generates a distinct cluster of seismicity in Southeast Alaska and drives ongoing mountain building in the Saint Elias Range.
Seismic Monitoring
The earthquake distribution shown in this map is derived from decades of seismographic monitoring by the Alaska Earthquake Center (AEC) at the University of Alaska Fairbanks and the USGS National Earthquake Information Center. The AEC's network of more than 300 seismometers continuously records ground motion throughout the state, enabling detection and location of earthquakes of magnitude 1.5 and above across most of Alaska.
For real-time earthquake information in Alaska and worldwide, the USGS Earthquake Hazards Program maintains interactive earthquake maps and the Did You Feel It? public reporting system. The Alaska Earthquake Center also provides a searchable earthquake catalog for researchers and the public.