Often, they begin with a subtle rumble that sounds like the approach of a truck. Shaking follows rattling nerves and cupboard dishes with equal velocity. Hopefully, little damage will occur outside of a few picture frames or living room knick-knacks, but sometimes Earth's crust just can't keep still, and a strong earthquake jolts Alaska.
What are earthquakes?
The violent release of energy along the planet's plates, shells of a sort that float on top of the mantle beneath the crust, is what most of us remember about earthquakes from high school science class. In Alaska, where the Pacific plate meets the oddly-shaped North American plate, that energy is released on a daily basis, seismic waves that feel to us like the rocking of a boat or the crash of a car, depending upon the epicenter, or location where the plates met and collided, and depth beneath us.
Why does Alaska have so many earthquakes?
Those two close-but-not-friendly Pacific and North American plates are constantly jockeying for position atop the mantle, and the Pacific plate is subducting, or sliding underneath, the North American one. Alaska also has several spots marking the boundaries of these plates: Southcentral Alaska, near Anchorage; the Interior, near Fairbanks; and along the Aleutian Chain. Faults can mark these boundaries, or be associated with them, and show up as cracks in the surface of the earth where rocks have been or are sliding past each other with relative regularity.
The Salcha, Fairbanks, Minto, and Denali faults are all fairly active.
How many earthquakes does Alaska have each year?
Alaska has 11% of the world's earthquakes, and 3 of the 6 largest in recorded history were located there. Since 1900, Alaska has had 1 magnitude 7 or 8 earthquakes per year, 45 earthquakes of magnitude 6 or 7, and 10,000 quakes overall annually. The most famous earthquake, of course, was the 1964 "Great Alaska Earthquake" centered near Prince William Sound. With a magnitude 9.2 over 4.5 minutes, this devastating temblor and resulting tsunami took the lives of 100 people and turned the city of Anchorage into a disaster area.
Smaller communities along Prince William Sound, like Valdez, were destroyed by the wave that struck, and the city now is located in an entirely new location about 6 miles from the original site.
I'm visiting Alaska soon; should I be worried?
No. Like any natural occurrence, Alaska's earthquakes are part of the state's landscape, fragile as it may be. The most important factor for anyone living in or visiting earthquake country is preparation. Alaska families are encouraged to build an "emergency kit" of food, water, fuel, and shelter for up to a week in case another earthquake of similar strength as 1964 strikes again. School children are taught the familiar "Duck, Cover, and Hold" mantra, hiding under desks during regular drills, and for those kids in coastal areas, practicing evacuation drills for tsunamis.
Note: On January 24, 2016, a magnitude 7.1 earthquake struck Cook Inlet about 100 miles south of Anchorage, causing minor damage to Anchorage but breaking gas and water lines on the Kenai Peninsula.
If your travels bring you to Alaska, there are tips for managing an earthquake, be it a tiny trembler or large shaker.
- Know your location. Are you near large buildings? The ocean? On a top floor of the hotel? Plan ahead for your evacuation, and ask the staff at hotels if they have an emergency protocol (nearly all do).
- Place your shoes, a jacket, keys, and cell phone next to or within reach of your bed. Remember, items will shake and sometimes fall during an earthquake, so you'll want to secure things as best you can before retiring for the night so you can grab them in a hurry.
- If an earthquake occurs and you are indoors, stay indoors. Do not run outside. Get under a bed, desk, or table, and cover your head. If there is nothing to hide under, go near an interior wall, get on the floor, and cover your head. Do not go near windows, large appliances, or cabinets. Stay there until the shaking stops completely, which could be a few seconds or a few minutes. If you are in a hotel or large public space, follow directions from staff or your tour guides for safe evacuation, if necessary. Be aware that sprinkler systems or fire alarms may be triggered by the shaking.
- If outdoors, move away from light poles, signs, or electrical wires, drop to the ground and cover your head. If you are driving, stay in your car and pull over as soon as possible. Do not exit the car until the shaking stops. If a power line should fall on or near your car, stay in the car and wait for help.