This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Carla Helfferich is a science writer at the Institute. Any Alaskan who lives south of the Brooks Range may encounter a singularly odd happening perhaps once every few years, or far too often in a single year. I'm wide awake, all systems flooded with adrenaline.
Many people can report similar experiences.
Something catches their attention, but it's not the heaving or quivering of an earthquake. Then everything began to shake. It turns out that what apparently warns us of an impending earthquake is actually the earthquake itself. More properly, our attention is caught by the arrival underfoot of the first of the different types of waves an earthquake can generate. Nearly all earthquakes large enough for people to feel start when the stress on some portion of the earth's crust exceeds the strength of the rock.