On Operational Earthquake Forecast and Prediction Problems

In his SSA presidential address (Jordan, 2014), and later in a more extended publication with coauthors (Jordan et al. , 2014), Jordan presents a vision of forecast and prediction problems of earthquake system science. As experienced practitioners and in full appreciation of scientific studies on earthquake forecasting, we find it necessary to share a complementary viewpoint. Eight decades ago, Richter (1935) introduced the logarithmic scale for sizing earthquakes, in full appreciation of the observed multiplicative scaling of energy liberated in a seismic event, inspired from the first statistics of the frequency of shocks of various magnitudes in southern California. In the 1960s, Edward Lorenz discovered deterministic chaos in a system of ordinary differential equations describing natural processes, Leon Knopoff demonstrated that a simple system of interacting elements may reproduce a complex “seismic” sequence, and Vladimir Keilis‐Borok posed the problem of seismology and logics. In the 1970s, Israel Gelfand and John Tukey independently created a culture of exploratory data analysis that permits overcoming (though not completely) the complexity of a process by robust representation of information and exhaustive numerical tests validating the results. By the 1980s, the lithosphere of the Earth was recognized as a complex hierarchically self‐organized nonlinear dissipative system with critical phase transitions through larger earthquakes (Keilis‐Borok, 1990). Mathematically, such chaotic systems are predictable—but only up to a limit and after substantial averaging: a success …