Reply to “Comment on ‘Is There a Basis for Preferring Characteristic Earthquakes over a Gutenberg–Richter Distribution in Probabilistic Earthquake Forecasting?’ by Tom Parsons and Eric L. Geist” by Jens-Uwe Klügel

The focus of Parsons and Geist (2009) was to test whether the key observational data used in earthquake forecasting necessitate a characteristic earthquake rupture model. The point of our article was not to suggest that a specific form of the Gutenberg–Richter earthquake distribution is a perfect representation of reality. The uncertainties surrounding event slip estimates, paleoseismic event rates, and observed a and b values in catalog magnitude–frequency distributions are broad. So broad, in fact, that giving full weight to just one model of earthquake rupture behavior in formal forecasting is unjustified. Further, the characteristic earthquake model requires definition of rupture segments, which introduces a series of unquantifiable uncertainties that are seldom addressed in forecasts (e.g., Field et al., 2009).