Violation of the scaling relation and non-Markovian nature of earthquake   aftershocks
  The statistical properties of earthquake aftershocks are studied. The scaling relation for the exponents of the Omori law and the power-law calm time distribution (i.e., the interoccurrence time distribution), which is valid if a sequence of aftershocks is a singular Markovian process, is carefully examined. Data analysis shows significant violation of the scaling relation, implying the non-Markovian nature of aftershocks. 
Sumiyoshi Abe (Mie University, Mie, Japan; ISMANS, Le Mans, France),   Norikazu Suzuki (Nihon University, Funabashi, Japan)