A distributed seismic system, “MyShake”, which collectively harnesses sensor data from smartphones to determine earthquake onset, and generate warnings through the self-same phone network. The system can record magnitude 2.5 or larger earthquakes, and provides on-phone detection capability to separate earthquake shake data from other every-day shakes of the phone. The earthquake data is collected at a central site where a network detection algorithm confirms that an earthquake is underway and estimates the location and magnitude in real-time. This information is used to issue an alert of forthcoming ground shaking, such as through the network of phones for an early earthquake warning system.