Across the region, as the ground begins to shake and windows rattle or objects fall from shelves, many people wake from sleep-while others are slower to sense the potential danger. These initial detections are followed rapidly by subsequent triggering of a dozen more instruments spread out both to the north, toward Seattle, and to the south, toward Portland, Ore.

Suddenly, multiple seismometers along the coast of Washington state are triggered as seismic waves emanate from a seconds-old earthquake. along the Pacific Northwest coast-it’s dark outside and most people are asleep indoors rather than alert and going about their day.