"Perhaps the scariest thing about an earthquake is that you don’t know when it’s going to hit. But what if you had a little warning? The California Integrated Seismic Network has been testing early warning systems statewide on the real-time seismic networks and have successfully been able to detect the shaking of an earthquake before it was felt, showing that seconds to tens-of-seconds of warning are possible. The CISN is now developing a prototype—called "ShakeAlert"—to provide warning to a small group of users. Learn about the methodologies, past performance, challenges and future plans for ShakeAlert. With Richard Allen, associate director of the Berkeley Seismological Laboratory."