Abstract

Determining the aperiodicity of large earthquake recurrences is key to forecast future rupture behaviour. Aperiodicity is classically expressed as the coefficient of variation of recurrence intervals, though the recent trend to express it as burstiness is more intuitive and avoids minor inaccuracies. Due to the underestimation of burstiness in records with a low number of recurrence intervals, the paradigm is to obtain long paleoseismic records with many events. Here we present a suite of synthetic paleoseismic records designed around the Weibull and inverse Gaussian distribution that demonstrate that age uncertainty relative to the mean recurrence interval causes overestimation of burstiness. The effects of over- and underestimation interact and produce increased likelihood for accurate estimates of aperiodicity with counterintuitive combinations of age uncertainty and number of recurrence intervals. Furthermore, we show that the way to calculate burstiness can have strong influences on the resulting statistic and its implication for probabilistic seismic hazard assessment. Comparing values of burstiness between paleoseismic records should therefore be done with caution.