Susan Hough at Asterisk:
Earthquake professionals have made major strides in forecasting the long-term average rate of earthquakes in any given region. Unlike predictions, which involve meaningfully useful bounds in time, space, and magnitude, forecasts are made in terms of probabilities that an earthquake of a certain size will strike on decadal or longer timescales. For example, in 2008, seismologists predicted that there is an estimated 99.7% chance that at least one magnitude 6.7 or greater earthquake will occur in California over the next 30 years. Based on long-term odds, seismologists are known to tell the public that “it’s not a question of if, it’s a question of when” a damaging earthquake will strike.
More here.