One of the dangers of an earthquake is they strike without warning. One time I was in Mexico and in the middle of the night the earth shook. While the damage to the hotel was minimal, I struggled to walk. My first reaction was to try to get out of the room. Fortunately, the quake stopped before I got very far. What could have been different if I had advanced warning? I could have stood under the door jam for extra protection, or ducked under the room desk for protection. In the past, early warning systems were science fiction.
Today, Early Warning Labs, a California start up company announced within three years they expect to release an early warning system.