Prediction VS Forecast

The official position of the USGS is even more emphatic: earthquakes cannot be predicted. “Neither the USGS nor Caltech nor any other scientists have ever predicted a major earthquake,” the organization’s Web site asserts.24 “They do not know how, and they do not expect to know how any time in the foreseeable future.”

Earthquakes cannot be predicted? This is a book about prediction, not a book that makes predictions, but I’m willing to stick my neck out: I predict that there will be more earthquakes in Japan next year than in New Jersey. And I predict that at some point in the next one hundred years, a major earthquake will hit somewhere in California.

Both the USGS and I are playing some semantic games. The terms “prediction” and “forecast” are employed differently in different fields; in some cases, they are interchangeable, but other disciplines differentiate them. No field is more sensitive to the distinction than seismology. If you’re speaking with a seismologist:

1. A prediction is a definitive and specific statement about when and where an earthquake will strike: a major earthquake will hit Kyoto, Japan, on June 28.

2. Whereas a forecast is a probabilistic statement, usually over a longer time scale: there is a 60 percent chance of an earthquake in Southern California over the next thirty years.

The USGS’s official position is that earthquakes cannot be predicted. They can, however, be forecasted.

Nate Silver, The Signal and the Noise (2012-09-27)

• forecast
• prediction
• semantics
• statistics