Why Alaska Has So Many Earthquakes: Plates, Faults and Records
Alaska has so many earthquakes because it sits on an active plate boundary, where the Pacific plate moves northwest and sinks beneath the North American plate along the Alaska-Aleutian subduction zone. The Alaska Earthquake Center processes generally 35,000 to 55,000 earthquakes a year, and the USGS says Alaska has more large earthquakes than the rest of the United States combined. The state also holds the US record: the magnitude 9.2 Great Alaska Earthquake of March 27, 1964.
What causes earthquakes in Alaska?
Most Alaska earthquakes come from two tectonic plates pressing against each other. According to the USGS, most seismic activity in Alaska results from the northwestward-moving Pacific plate pushing into the corner of the North American plate that holds Alaska.
The way the plates meet changes along the coast. In the southeastern panhandle, the USGS describes the plates sliding past each other on strike-slip faults. From Yakutat Bay westward, the Pacific plate collides with Alaska. West of Kayak Island, that collision becomes subduction: the Pacific plate dives beneath continental Alaska and the Aleutian Islands.
The plates move quickly by geologic standards. The Alaska Division of Geological & Geophysical Surveys (DGGS) gives a rate of about 2 inches (5.5 cm) or more per year for the Pacific plate relative to the North American plate. USGS event summaries list about 2.2 inches (57 mm) per year near Anchorage and about 2.5 inches (64 mm) per year off the Alaska Peninsula.
Between Kayak Island and Yakutat Bay, the USGS says the Pacific plate is mostly locked to southern Alaska. That coupling has pushed up the coastal St. Elias Mountains. It also sends compressive stress inland as far as Fairbanks, and that stress drives slip on the Denali fault.
What kinds of earthquakes does Alaska get?
USGS Alaska Science Center research groups the subduction zone’s hazards into megathrust, intraslab and crustal earthquake sources. Southeast Alaska adds a fourth source, the Queen Charlotte-Fairweather fault system.
| Type | Where it happens | Example (USGS) |
|---|---|---|
| Megathrust | On the plate boundary where the Pacific plate slides under Alaska | M9.2 Prince William Sound, March 27, 1964; M8.2 Chignik, July 28, 2021 (local time) |
| Intraslab | Inside the sinking Pacific plate, tens of kilometers down | M7.1 north of Anchorage, November 30, 2018 |
| Crustal | On faults in the North American plate, close to the surface | M7.9 Denali fault, November 3, 2002 |
| Strike-slip boundary | Queen Charlotte-Fairweather fault system in southeast Alaska | USGS says it has produced large earthquakes affecting Canada and the US over the last 100 years |
The 2018 Anchorage earthquake shows how the deeper type works. The USGS says it ruptured a fault inside the subducting Pacific slab, not the shallower plate interface, and its catalog lists a depth of about 47 km (29 miles). It damaged two hospitals, several schools and many roads, with damage estimated at $30 million. Our guide to earthquake depth explains why depth changes how a quake is felt.
The 2002 Denali fault earthquake shows the crustal type. The USGS reports surface rupture of about 300 km (about 190 miles) and a maximum offset of 8.8 meters (29 feet) near the Tok Cutoff Highway. Some supports on the Trans-Alaska Pipeline were damaged, and pipeline operation was suspended temporarily.
How many earthquakes happen in Alaska each year?
The Alaska Earthquake Center at the University of Alaska Fairbanks processes generally 35,000 to 55,000 earthquakes a year. That figure comes from the center’s 2025 seismicity year in review, published April 3, 2026. Most of these events are too small to feel. Since 2016, about 200 earthquakes a year have been reported felt somewhere in the state.
| Earthquake size | Typical number | Source |
|---|---|---|
| All events processed | 35,000 to 55,000 per year | Alaska Earthquake Center |
| Magnitude 3 and larger | Close to 2,000 per year (2025 was a bit above average) | Alaska Earthquake Center |
| Magnitude 5 and larger | 50 to 75 per year | Alaska Earthquake Center |
| Magnitude 6 to 7 | About six per year (average since 1900) | Alaska Seismic Hazards Safety Commission |
| Magnitude 8 and larger | One every 13 years on average (since 1900) | Alaska Seismic Hazards Safety Commission, DGGS |
State sources differ on magnitude 7 events. The Alaska Seismic Hazards Safety Commission lists one magnitude 7 to 8 earthquake per year since 1900, while DGGS gives one every two years. The commission also states that Alaska has 11 percent of the world’s recorded earthquakes.
The largest Alaska earthquake of 2025 was a magnitude 7.3 near Sand Point on July 16, according to the Alaska Earthquake Center. It prompted a tsunami warning, but no notable tsunami followed. A magnitude 7 struck beneath Hubbard Glacier near the Canadian border on December 6, 2025.
What happened in the 1964 Great Alaska Earthquake?
The Great Alaska Earthquake struck at 5:36 p.m. local time on March 27, 1964 (March 28 at 03:36 UTC), with magnitude 9.2. The USGS event page places the epicenter about 6 miles (10 km) east of the mouth of College Fiord in Prince William Sound. The rupture started about 25 km (16 miles) below the surface. Shaking lasted about 4.5 minutes.
The USGS calls it the most powerful recorded earthquake in US history. It is the second-largest earthquake ever recorded, after the magnitude 9.5 Chile earthquake of 1960. DGGS says it ruptured a patch of the subduction zone about 500 miles (about 800 km) long.
The earthquake and its tsunamis took 131 lives, 122 of them from tsunamis, according to the USGS catalog. Property loss was about $311 million in 1964 dollars. In Anchorage, the Turnagain Heights landslide destroyed about 75 houses.
Which other large earthquakes has Alaska had?
Alaska holds most of the largest earthquakes on the US list. These examples come from the USGS earthquake catalog (dates in UTC):
- M8.7, February 4, 1965, Rat Islands: the USGS notes a tsunami reported about 10.7 meters (35 feet) high on Shemya Island.
- M8.6, March 9, 1957, Andreanof Islands: the tsunami reached Hawaii and caused about $5 million in property damage there.
- M8.6, April 1, 1946, Unimak Island: the tsunami destroyed the Scotch Cap Lighthouse and killed 159 people in Hilo, Hawaii.
- M8.2, July 29, 2021, Chignik: the USGS says its remote location resulted in little impact to people and infrastructure.
- M7.8, July 10, 1958, Lituya Bay: the largest earthquake in southeast Alaska since 1899; the USGS says a rockslide at the head of the bay caused water to surge about 530 meters (1,740 feet).
The full ranking is in our guide to the largest earthquakes in US history.
How can you check the latest Alaska earthquakes?
- Open the Alaska Earthquake Center’s earthquake map at earthquake.alaska.edu. It is the state’s own earthquake catalog.
- Check the USGS event page for the magnitude type, depth and tsunami flag. Our guide on how to read a USGS earthquake report walks through each field.
- See our live list of USGS earthquakes in Alaska for the last 24 hours, 7 days and 30 days in one place.
- For tsunami messages, the official source is tsunami.gov. Our tsunami page lists the latest NTWC and PTWC messages, and our guide to what causes a tsunami explains why most earthquakes do not produce one.
Our pages show official data and are not a warning service. For safety guidance, follow local emergency officials and the National Weather Service.
Bottom line
Alaska is the most seismically active state because the Pacific plate is moving into and beneath it at roughly 2 to 2.5 inches a year. That one boundary produces shallow megathrust quakes, deep quakes inside the sinking plate and crustal quakes on faults like the Denali. The Alaska Earthquake Center processes tens of thousands of events a year, and the largest of them, the 1964 magnitude 9.2, is still the US record.
FAQ
Does Alaska have more earthquakes than California?
For large earthquakes, yes. The USGS says Alaska has more large earthquakes than the rest of the United States combined. The Alaska Seismic Hazards Safety Commission states that Alaska has 11 percent of the world’s recorded earthquakes.
What was the biggest earthquake in Alaska?
The biggest was the magnitude 9.2 Great Alaska Earthquake on March 27, 1964, in Prince William Sound. It is the largest recorded earthquake in US history and the second-largest recorded anywhere.
How often does Alaska have a magnitude 8 earthquake?
Since 1900, Alaska has averaged one magnitude 8 or larger earthquake every 13 years, according to the Alaska Seismic Hazards Safety Commission and DGGS. This is a long-term average, not a schedule.
Why are most Alaska earthquakes not felt?
Most are small: of the tens of thousands processed each year, about 200 are reported felt. Many larger ones strike offshore or in remote areas, as with the 2021 magnitude 8.2 Chignik earthquake.