Stress Triggering and Earthquake Probability Estimates

Jeanne L. Hardebeck

Published April 2004, SCEC Contribution #764

Stress triggering and fault interaction concepts are beginning to be incorporated into quantitative earthquake probability estimates. However, the current methods are limited in their range of compatible earthquake nucleation models. I introduce a new general method for translating stress changes into earthquake probability changes, which can potentially be used with any physical fault model. Given the large uncertainties in earthquake probability calculations, it is unclear whether the small probability changes resulting from stress transfer are significant and meaningful for the purposes of seismic hazard assessment. I present a case study of the effect of the 1992 M7.3 Landers, California, earthquake on the probability of a major earthquake on the San Andreas Fault in southern California. This is a large event in a well-studied region, which should maximize the probability change signal and minimize the uncertainty. Even for this scenario, the earthquake probability change for a 30 year period is not significant with respect to the initial uncertainty in the earthquake probability. This example, comparisons with other studies, and exploration of parameter space imply that the probability changes due to stress triggering are significant only for time intervals which are short compared to the repeat time of the target fault. Therefore stress change calculations will be useful in long-term seismic hazard assessment only for low slip-rate faults. Otherwise, stress triggering calculations are best utilized in the short-term immediately following a major earthquake.

Hardebeck, J. L. (2004). Stress Triggering and Earthquake Probability Estimates. Journal of Geophysical Research, 109(B04310). doi: 10.1029/2003JB002437.