An earthquake early warning system being tested in California gave seismologists in Pasadena up to 30 seconds to prepare for Monday morning’s temblor in the desert of Riverside County.

“It was right,” said Kate Hutton, a seismologist with Caltech. “I sat really still to see if I could feel it and it worked.”

The Early Earthquake Warning project, a test run of a proposed statewide program that would use thousands of sensors already in place to notify people about imminent shaking from moderate to strong earthquakes, alerted Caltech scientists about a 4.7 temblor in Anza.

An early warning would give utilities time to shut down, trains a chance to slow so they don’t derail and workers a chance to move away from hazardous materials or precarious positions.