Quasi-periodic recurrence of large earthquakes on the southern San Andreas fault

Katherine M. Scharer, Glenn P. Biasi, Ray J. Weldon, & Thomas E. Fumal

Published 2010, SCEC Contribution #1291

It has been 153 years since the last large earthquake on the southern San Andreas fault, but the average interseismic interval is only ~100 yr. If the recurrence of large earthquakes is periodic, rather than random or clustered, the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses. Unfortunately, robust characterization of a distribution describing earthquake recurrence on a single fault is limited by the brevity of most earthquake records. Here we use statistical tests on a 3000 yr combined record of 29 ground-rupturing earthquakes from Wrightwood, California. We show that earthquake recurrence there is more regular than expected from a Poisson distribution and is not clustered, leading us to conclude that recurrence is quasi-periodic. The observation of unimodal time dependence is persistent across an observationally-based sensitivity analysis which critically examines alternative interpretations of the geologic record. The results support formal forecast efforts which use renewal models to estimate probabilities of future earthquakes on the southern San Andreas fault. Only four intervals (15%) from the record are longer than the present open interval, highlighting the current hazard posed by this fault.

Citation
Scharer, K. M., Biasi, G. P., Weldon, R. J., & Fumal, T. E. (2010). Quasi-periodic recurrence of large earthquakes on the southern San Andreas fault. Geology, 555-558.