# Archive ouverte HAL – The influence of the brittle-ductile transition zone on aftershock and foreshock occurrence

### Giuseppe Petrillo ^{1} Eugenio Lippiello ^{1} François Landes ^{2} Alberto Rosso ^{3}

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Giuseppe Petrillo, Eugenio Lippiello, François Landes, Alberto Rosso. The influence of the brittle-ductile transition zone on aftershock and foreshock occurrence. *Nature Communications*, Nature Publishing Group, 2020. ⟨hal-02908552⟩

Aftershock occurrence is characterized by scaling behaviors with quite universal exponents. At the same time, deviations from universality have been proposed as a tool to discriminate aftershocks from foreshocks. Here we show that the change in rheological behavior of the crust, from velocity weakening to velocity strengthening, represents a viable mechanism to explain statistical features of both aftershocks and foreshocks. More precisely, we present a model of the seismic fault described as a velocity weakening elastic layer coupled to a velocity strengthening visco-elastic layer. We show that the statistical properties of aftershocks in instrumental catalogs are recovered at a quantitative level, quite independently of the value of model parameters. We also find that large earthquakes are often anticipated by a preparatory phase characterized by the occurrence of foreshocks. Their magnitude distribution is significantly flatter than the aftershock one, in agreement with recent results for forecasting tools based on foreshocks.

- 1. Department of Mathematics and Physics [Caserta]
- 2. LRI - Laboratoire de Recherche en Informatique
- 3. LPTMS - Laboratoire de Physique Théorique et Modèles Statistiques