Fault Heterogeneity and the Connection between Aftershocks and Afterslip – Archive ouverte HAL

Eugenio Lippiello 1 Giuseppe Petrillo 1 François Landes 2, 3, 4 Alberto Rosso 5

Eugenio Lippiello, Giuseppe Petrillo, François Landes, Alberto Rosso. Fault Heterogeneity and the Connection between Aftershocks and Afterslip. Bulletin of the Seismological Society of America, Seismological Society of America, 2019, 109 (3), pp.1156-1163. ⟨10.1785/0120180244⟩. ⟨hal-02156407⟩

Whether aftershocks originate directly from the mainshock and surrounding stress environment or from afterslip dynamics is crucial to the understanding of the nature of aftershocks. We build on a classical description of the fault and creeping regions as two blocks connected elastically, subject to different friction laws. We show analytically that, upon introduction of variability in the fault plane’s static friction threshold, a non trivial stick-slip dynamics ensues. In particular we support the hypothesis that the aftershock occurrence rate is proportional to the afterslip rate, up to a corrective factor that is also computed. Thus, the Omori law originates from the afterslip’s logarithmic evolution in the velocity-strengthening region. We confirm these analytical results with numerical simulations, generating synthetic catalogs with statistical features in good agreement with instrumental catalogs. In particular we recover the Gutenberg-Richter law with a realistic b-value (b'1) when Coulomb stress thresholds obey a power law distribution.

  • 1. Department of Mathematics and Physics [Caserta]
  • 2. LRI - Laboratoire de Recherche en Informatique
  • 3. TAU - TAckling the Underspecified
  • 4. UP11 UFR Sciences - Université Paris-Sud 11 - Faculté des Sciences
  • 5. LPTMS - Laboratoire de Physique Théorique et Modèles Statistiques