ShakeAlert issued a warning 5.4 seconds after the beginning of the 6.0 magnitude earthquake that hit the Napa region on August 24 , 2014 . Although it was initially reported that the system provided 10 seconds of warning before the S-wave arrived in Berkeley , subsequent information showed that this was in error and the warning arrived only 5 seconds before the S-wave in Berkeley . This means the S-waves had already arrived in Napa and Vallejo when the warning was issued . San Francisco received 8 seconds warning
6.0 magnitude earthquake
2014 South Napa earthquake
ShakeAlert