The strong earthquake that sent panicked Alaskans, fearing a tsunami, to high ground early Tuesday is a reminder that, at least around the Pacific Rim, the biggest danger from quakes often comes not from the land but from the sea.

Given the need for speed — deadly waves can strike within minutes in some cases — tsunami forecasters tend to shoot first and ask questions later, sending out broad alerts that are often scaled back or canceled within hours.

In the case of Tuesday’s quake, waves could have struck the nearest land, Kodiak Island, within half an hour. The U.S. Tsunami Warning Center, one of two operated by NOAA, sent out its first alerts within 3 minutes of the event, a typical time frame, said Michael Angove, who manages the tsunami program at the National Oceanic and Atmospheric Administration.

The quake Tuesday turned out to be largely harmless, a function of its 7.9 magnitude, which made it about 100 times less powerful than the world’s strongest earthquakes, and its location in the Gulf of Alaska about 170 miles from Kodiak Island.