Smartphones across San Francisco blared Thursday morning as an emergency alert warned residents about a potential tsunami in the wake of a major earthquake off the North Coast of California. That alert should have been accompanied by loud sirens,

Longtime residents of San Francisco noticed something missing from the city's emergency response to Thursday's tsunami warning after a 7.0 magnitude earthquake off the Northern California coast: the old system of emergency sirens were silent.

San Francisco's Department of Emergency Management previously used the sirens to run weekly tests at noon on Tuesdays.

Thursday's tsunami warning was a real test for people living near the coast. Many did get an alert after the quake, but it turns out a critical warning system in San Francisco was not working. Amanda Hari reports.

A tsunami warning for the San Francisco coast was lifted after sparking panic following a 7.0 magnitude earthquake. The National Weather Service issued the alert after a quake struck near Eureka, Northern California,