Major Quake Almost Inevitable For California - Study US: April 15, 2008 LOS ANGELES - California will almost inevitably be struck by a major earthquake, and possibly a catastrophic quake, sometime in the next 30 years, scientists said on Monday in the most comprehensive geologic forecast for the state. California faces a more than 99 percent chance of being hit by a magnitude 6.7 temblor -- the size of the 1994 Northridge quake -- in the next 30 years, according to a study using new data and analyzing earthquake probabilities across the state.