Maximum Earthquake Magnitude at Fault

Abstract

The maximum possible magnitude of earthquakes that can be generated by slip on any given geologic fault is a function of many characteristics of the fault. Semi‐empirical formulas are available relating the maximum possible magnitude to the nature of fault slips, to potential rupture‐surface length, to its area, to the slip rate, and to the maximum paleoseismic slip. We can also obtain expert estimates of the maximum magnitude, based on observation of other parameters. Bayesian criteria are developed for combining the various estimates for any given fault and for incorporating data about the magnitudes of past earthquakes. These criteria are applied to Mexican subduction earthquakes, pointing out the weaknesses of the approach and the need for semiempirical formulas applicable to conditions such as those under the Valley of Mexico, where the interaction of approximately orthogonal systems of faults leads to the need of fresh‐rock breakage associated with every new moderate earthquake.