A new phone app uses vibrations from smartphones to alert people about earthquakes. The phone app recognizes sudden shaking of the earth's surface through sensors in smartphones. The new app is called MyShake. It is the work of four researchers at the University of California, Berkeley. They said they created a worldwide warning system that would inform people and give them time to prepare. Other earthquake apps include QuakeFeed, Quakes and Earthquake. They show where earthquakes have happened, at what strength, and the aftershocks. Those use data from the U.S. Geological Survey. The MyShake app is available only for Android phones. Smart phones are equipped with accelerometers. These instruments measure movement, like that of a car or airplane. They can also measure the shaking of a machine, building or other structure. Accelerometers are used in activity trackers.