When will it happen again?
Another Large Quake in the next 100 years? Maybe, but..."
Based on models taking into account the long-term rate of slip on the San Andreas fault and the amount of offset that occurred on the fault in 1906, the best guess is that 1906-type earthquakes occur at intervals of about 200 years.
Because of the time needed to accumulate slip equal to a 20 ft offset, there is only a small chance (about 2 percent) that such an earthquake could occur in the next 30 years, according to the report of the Working Group on California Earthquake Probabilities.
The real threat to the San Francisco Bay region over the next 30 years comes not from a 1906-type earthquake, but from smaller (magnitude about 7) earthquakes occurring on the Hayward fault, the Peninsula segment of the San Andreas fault, or the Rodgers Creek fault.
Probabilities (shown in boxes) of one or more major (M>=6.7) earthquakes on faults in the San Francisco Bay Region during the coming 30 years. The threat of earthquakes extends across the entire San Francisco Bay region, and a major quake is likely before 2032. Knowing this will help people make informed decisions as they continue to prepare for future quakes.
Long-term regional probability estimates from the 1999 Working Group on California Earthquake Probabilities.
The Great 1906 San Francisco Earthquake is the most powerful in Northern California's recorded history. New studies of this earthquake are yielding important clues about how and when such events occur. With this improved knowledge we can better prepare for future strong temblors.