New empirical tests of the multifractal Omori law for Taiwan

Abstract

We report new tests on the Taiwan earthquake catalog of the prediction by the Multifractal Stress Activation (MSA) model that the p-value of the Omori law for the rate of aftershocks following a mainshock is an increasing function of its magnitude Mm. This effort is motivated by the quest to validate this crucial prediction of the MSA model and to investigate its possible dependence on local tectonic conditions. With careful attention to the long-term as well as short-term time-dependent magnitude completeness of the Taiwan catalog, and with the use of three different declustering techniques, we confirm the universality of the prediction p(Mm) = (0.09 \pm 0.03) \times Mm + (0.47 \pm 0.10), valid for the SCEC Southern California catalog, the Harvard-CMT worldwide catalog, the JMA Japan catalog and the Taiwan catalog. The observed deviations of the two coefficients of the p(Mm) linear dependence on Mm from catalog to catalog are not significant enough to correlate meaningfully with any tectonic features.