The main digital infrastructure that matters is people. The USGS estimates [1]:
"A repeat of the 1906 magnitude 7.9 earthquake, the worst case scenario for the Bay Area, is estimated to result in
about 5800 fatalities if it strikes during working hours. Most scenarios, however, have maximum projected fatalities on the order of several hundred, reflecting the success of earthquake-resistant design and construction practices in California, particularly in residences. The loss of life is predicted to be highest if an earthquake occurs in the early afternoon when people are working in commercial buildings with varying vulnerability to quakes These predicted mid-afternoon fatalities are generally about 5 times higher than values predicted at 2:00 AM when the population is assumed to be in wood frame residential units."
"A repeat of the 1906 magnitude 7.9 earthquake, the worst case scenario for the Bay Area, is estimated to result in about 5800 fatalities if it strikes during working hours. Most scenarios, however, have maximum projected fatalities on the order of several hundred, reflecting the success of earthquake-resistant design and construction practices in California, particularly in residences. The loss of life is predicted to be highest if an earthquake occurs in the early afternoon when people are working in commercial buildings with varying vulnerability to quakes These predicted mid-afternoon fatalities are generally about 5 times higher than values predicted at 2:00 AM when the population is assumed to be in wood frame residential units."
[1] http://earthquake.usgs.gov/regional/nca/wg02/losses.php