Did he give a number? 5% may be about right. There are a number of doublets of M7+ earthquakes around the western part of the Ring of Fire.

Kerry buys some leeway from criticism by having nearly single-handedly elevating trenching and paleoseismology into the tool of choice to reconstruct the history of earthquakes on most of the active faults in California. He with his students and other paleoseismologists have charted the recurrence intervals on dozens of faults around the world, so he has some idea what he is talking about, although the time scales he can resolve in a trench are decades, not weeks.

Like Tom Rockwell and David Schwartz, when he talks, we listen.