United States

This app did not send an early warning about the California quake. Officials said it worked as designed

(CNN)People in Los Angeles are wondering why their phones didn't warn them before the ground started shaking on Thursday.An earthquake quake detection app released by the city of Los Angeles earlier this year did not alert its users when a 6.4 quake struck near Ridgecrest, a desert town about 150 miles away. But officials say it was not a failure. The ShakeAlertLA app, which is connected to the US Geological Survey's network of early warning sensors, is set to alert cellphone users when the system senses an earthquake of magnitude 5.0 or greater, or with potentially damaging shaking, within Los Angeles County.While Thursday's quake was greater than magnitude 5 in Kern County, in Los Angeles the shaking was below 4.5, the city said."The sys ...