Generally, there’s a low risk of a large tsunami hitting Juneau.<\/p>\n
There aren’t tsunami sirens in town, as City and Borough of Juneau Emergency Programs Manager Tom Mattice explained, because the city doesn’t qualify for a siren system by federal government standards. A new study might force Mattice and the federal government to reexamine that likelihood, though.<\/p>\n
The study, done by the Alaska Division of Geological &Geophysical Surveys, includes a series of maps and hypothetical worst-case scenarios<\/a> concerning what they call landslide-generated tsunamis, and released their findings last week. These kinds of submarine landslides have not been studied much, but they can be extremely dangerous.<\/p>\n Offshore tsunamis, the ones we hear about the most, are caused by large, sudden movements of the ocean floor and often start out in the ocean. Therefore, tsunami warning systems and evacuation plans can be put into place and people can be warned. With an inshore\/landslide-generated tsunami, they can start in a matter of moments.<\/p>\n “When that occurs, there’s no emergency alert system,” Mattice said. “There’s no buoy system. There’s nothing telling us it’s coming.”<\/p>\n It’s difficult to fully comprehend what these tsunamis would look like. Mattice said a major earthquake could cause an underwater landslide (what he calls a “slump”) at locations throughout the area that are prone to this. Mattice said that Juneau, with glacial rebound and steep shorelines, has a couple of areas that are vulnerable. In a release from the CBJ, Mattice said this study helps him and his staff better “understand evacuation areas and response.”<\/p>\n [Expert: Juneau tsunami unlikely<\/a>]<\/ins><\/p>\n The main area detailed in the report is at Fritz Cove, where an underwater slump could cause sea levels to raise by 40 or 50 feet. If this happens at low tide, it might not be a terribly destructive event, Mattice said. With Fritz Cove located near the Juneau International Airport, though, an inshore tsunami at high tide could be disastrous.<\/p>\n “A 40-foot run-up on a king tide is gonna take out your airport,” Mattice said.<\/p>\n Other areas in town at risk, according to the report, are Berners Bay, Eagle River, Sheep Creek and South Franklin Street. If a landslide-generated tsunami begins in the Taku Inlet, the report detailed, it could create a rise in sea level of 35-45 feet but would run out of energy as it rebounded down Gastineau Channel and reach downtown in six or seven minutes with a rise in sea level of 6-10 feet.<\/p>\n Mattice posted two maps on the city’s website, one detailing how much water levels could rise from an offshore tsunami<\/a> and how much they could rise from a submarine landslide<\/a>. The worst-case scenarios for an offshore tsunami, according to these maps, is up to about 16 feet. The worst-case scenarios for submarine landslides is about 52 feet.<\/p>\n