Large earthquakes are caused by the sudden release of accumulated stresses between crustal plates that move against each other on the earth's surface. Earthquakes are of concern in Juneau because of the city's proximity to large fault systems as well as the likelihood of landslides, avalanches and tsunamis resulting from a significant earthquake.
Although most of Alaska's earthquakes occur in the Southcentral and Southwest regions, Southeast Alaska experiences earthquakes from the Queen Charlotte-Fairweather fault, which runs northwest to southeast in close proximity to Juneau. The Fairweather fault system has caused three recent moderate to large earthquakes: a magnitude 8.1 earthquake in 1949, a magnitude 7.9 event in 1958 that triggered the giant landslide-generated wave in Lituya Bay, and a magnitude 7.6 quake in 1972.
Much of the damage in large earthquakes in Alaska is caused by soil liquefaction. Juneau's soils have not yet been assessed for liquefaction, but it is likely that floodplains, such as the Mendenhall Valley, are potentially at risk. Because of the steep slopes around Juneau, landslide-induced tsunamis are also possible if an earthquake triggers a large landslide.
What You Can Do
- Pick "safe places" in each room of your home. Injury statistics show that people who move during quakes are more likely to be injured. Also pick safe places in your office or school, or any other buildings you frequent.
- Practice drop, cover, and hold in each safe place. Practice these actions so that they become automatic response. Responding quickly and automatically may help protect you from injury.
- Secure items in your home that might fall, such as pictures or sculptures.
- Install strong latches or bolts on cabinets.
- Hang heavy items, such as pictures and mirrors, away from beds, couches, and anywhere people sit.
- Talk to your insurance agent about earthquake protection.
- Brace overhead light fixtures. During earthquakes, overhead light fixtures are the most common items to fall.
- Strap your water heater to wall studs. The water heater may be your best source of drinkable water following an earthquake. Protect it from damage and leaks.
- Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects. Earthquakes can turn cracks into ruptures and make smaller problems bigger.
- Check to see if your house is bolted to its foundation. Homes bolted to their foundations are less likely to be severely damaged during earthquakes. Homes that are not bolted can slide off their foundations and usually must be condemned.
- Consider having your building evaluated by a professional structural design engineer.
- Check propane and fuel tank fittings after earthquakes, and always have tools nearby for an emergency shutoff.