The track record for predictions based on time since the last earthquake and its magnitude (Parkfield, Nishenko, etc.) is not good.

Probably "predictions" based on more solid ground. Omori's law for aftershocks from the quakes that have already occurred, and the background rate of very large earthquakes every century or so, are the two numbers that matter here. Much like the recent, very conservative forecasts put on line by Lucy Jones and company.

John