Halfway through 2018, January's magnitude 7.9 earthquake in the Gulf of Alaska remains the year's largest quake worldwide.
For decades, there have been tantalizing clues about how we might know when an earthquake will happen. Sometimes, clusters of small earthquakes called foreshock sequences come in the days or weeks before a large earthquake.
Alaska's most recent deadly tsunami struck without warning on November 3, 1994. Witnesses described new steel sheet piles snapping in half as the railway dock, which was being refurbished, suddenly slid away from the shore.