This Is the Biggest Earthquake to Ever Shake Alaska

On average, Alaska experiences more earthquakes than any other state. The state has had a greater number of significant earthquakes than all others combined. Discover the biggest earthquake to ever shake Alaska and find out how strong it was, where it occurred, and where it ranks among the most powerful seismic events in the country. Also, learn why we may never have a cut-and-dry answer about the strongest earthquake to strike The Last Frontier.

What Was the Most Powerful Earthquake to Ever Shake Alaska

The most powerful earthquake to ever shake Alaska was a 9.2 M_w event. This earthquake struck the state on March 27, 1964, at 5:36 p.m. local time. The event’s epicenter was 60.908°N 147.339°W in Chugach, about 85 miles east-southeast of Anchorage.

The devastating earthquake triggered landslides and tsunamis throughout Alaska and far beyond. The impacts of the tsunamis hit remote places as far away as Japan and Hawaii. The quake occurred deep underground at a depth of 16 miles and lasted for between 4 and 5 minutes, all the time needed to devastate the area.

The aftershocks that followed the main shock were powerful. Almost a dozen aftershocks greater than 6.0 M_w rocked the area over the next 24 hours. That means just the aftershocks from this earthquake were stronger than the most powerful earthquake to strike places like Oklahoma.

What Caused the 1964 Alaska Earthquake?   

The most powerful earthquake to ever shake Alaska was a megathrust event. Megathrust earthquakes are large events that occur in subduction zones where one tectonic plate is forced below another. In this case, the Aleutian subduction zone was the fault responsible for generating the earthquake.

At the Aleutian Trench, the Pacific plate is subducted below the North American plate. This area is responsible for some of the largest, most devastating earthquakes in the world. 

Where Is the Epicenter on a Map?

Officially, the epicenter of the most powerful earthquake to ever shake Alaska was located at 60.908°N 147.339°W. This is a part of Alaska called Chugach. This is in the southeastern part of the main body of Alaska, but not in the state’s panhandle.

The quake’s epicenter is about 85 miles east-southeast of Anchorage and about 45 miles east-northeast of Whittier. Just south of this area is the Prince William Sound, a body of water that was greatly impacted by the seismic event. 

Although this part of the world may seem remote, the earthquake unleashed devastating effects upon the immediate area and some places very far away.

How Much Damage Did the Earthquake Do?

The earthquake was unbelievably powerful. An area measuring about 180,000 square miles, larger than the state of California, was directly affected by the quake. Some parts of Alaska sank by as much as 8 feet, and some parts of the state rose by over 30 feet.

The quake caused over $300 million in damage, worth almost $3 billion in 2022. The shaking, large fissures, uplifting and sinking landmasses, tsunamis, and landslides caused by the quake tore towns apart.

The maximum intensity on the Modified Mercalli intensity scale reached XI, an extreme event and the second-highest rating available on the scale.

Many buildings collapsed in the earthquake, but others were wrecked by the landslides and tsunamis that followed. Portage and Girdwood were destroyed, Anchorage was heavily damaged, and several ports near the epicenter were wrecked.

The Casualties from the 1964 Alaska Earthquake

The earthquake killed at least 131 people. The earthquake itself killed 9 people, but the tsunamis and landslides spawned by the biggest earthquake to ever shake Alaska killed 122 others. Most of the people killed by the earthquake died in Alaska. However, the quake’s impacts were far-reaching. A dozen people died in California and 5 died in Oregon. The weeks and months following the earthquake were filled with powerful aftershocks.

While the earthquake was simply terrible in its size and impact, scientists learned a great deal about megathrust events as a result of studying the event.

A Potential Tie for the Biggest Earthquake to Strike Alaska

Although we have listed the 1964 Alaska earthquake as the biggest earthquake to ever shake Alaska, the record may be a tie. Scientists studying the impacts of a seismic event using records of a far-reaching tsunami taken back in 1585 postulate that an equally powerful or slightly more powerful earthquake occurred in the Aleutian Islands centuries ago.

Some evidence suggests that the same megathrust event that occurred in 1964 also happened nearly four centuries before. The tsunami devastated parts of Hawaii, and a tsunami wave measuring 6 feet tall struck as far away as Japan. However, evidence of this earthquake is sparse, so we’re not going to give it the top spot on our list.

The biggest earthquake to ever shake Alaska was a powerful event that destroyed homes and killed over 100 people. This was the most powerful recorded earthquake in North America. Given the seismic situation in the Aleutian subduction zone, such an event may happen again in the future. Hopefully, it’s not as powerful and deadly as the one in 1964.

The photo featured at the top of this post is © Inked Pixels/Shutterstock.com