Here's the good news: The huge 7.9 quake that hit off the shores of Alaska's Aleutian Islands last week didn't cause a lot of damage, and the alert issued by the National Tsunami Warning Center turned out to be unnecessary.
As io9 reported, the seismic event struck in a mostly-uninhabited segment of the islands, and it occurred so deep in the earth - about 71 miles down - that it didn't produce enough surface displacement to trigger a major tsunami.
Okay, great. But now, here's the bad news. The Los Angeles Times reminded us that a 2013 study by the U.S. Geological Survey warned that a 9.1 quake, the size of the one that occurred in Alaska in 1964, might unleash a tsunami so powerful that it would threaten the California coast, force mass evacuations and potentially cause billions of dollars in economic losses.
In the study, researchers used a computer simulation to gauge the impact of a quake that was the same size as the 1964 event but located in a different place - between Kodiak Island and the Shumagin Islands off the Pacific coast of the Alaskan peninsula. As they noted, there are similarities between the geology and tectonic settings of that spot and the area of Prince William Sound where the 1964 quake occurred, so it's plausible that that it could generate a massive quake that would have wider effects.