Why can’t we predict earthquakes?

Photo: Peter Holderness/Caltech

“There are 50 earthquakes in California today. You don’t want me to predict every one of them. You want a prediction of which of the 20, 30, 40,000 earthquakes we will record this year is going to be the one large enough to actually do some damage. So we don’t want prediction of just the time of an earthquake. We want prediction of the magnitude of the earthquake, but the magnitude … is determined by the length of the fault that moves in the event. And it doesn’t move over the whole fault at once. It starts at a point and moves down the fault until it hits something that makes it stop. And that determines how big the earthquake is going to be. So it may be … that the earth doesn’t have the information about how big an earthquake will be before it begins.”

—Seismologist and science communicator Lucy Jones, a visiting associate in geophysics at Caltech, answered this question and others on the Caltech Science Exchange. Find out more at scienceexchange.caltech.edu.