LOS ANGELES — California’s new earthquake early warning cellphone app issued its first public alert when a modest tremor occurred this week in a rural area of the state, a newspaper reported.

MyShake app project manager Jennifer Strauss said more than 40 people received the warning when a 4.3 magnitude quake struck Tuesday morning in mountains between the central coast and the San Joaquin Valley, the Los Angeles Times said.

The MyShake app was developed by the University of California, Berkeley, and released in October.

It is designed to quickly take data from seismic sensors and send warnings to potentially affected areas if a quake of magnitude 4.5 or greater occurs and if the projected shaking at a particular location is at a certain level of intensity.

It sent the warning Tuesday because the initial reading was magnitude 4.8.

The quake was centered in the rural Cholame Valley. It was felt in the city of Paso Robles more than 20 miles (32 kilometers) away but shaking there was very mild.

The app is expected to be most effective for areas some distance from the epicenter where the warning can be received before strong shaking arrives and protective actions can be taken.

A similar app called ShakeAlertLA was developed for the city of Los Angeles and released about a year ago.