Analysis of the 2012 Ahar-Varzeghan (Iran) seismic sequence: Insights from statistical and stress transfer modeling

In order to analyze the spatial distribution of the sequence, new source models are proposed for the two main shocks. For the first shock, the coseismic slip distribution is constrained by the available data on surface ruptures. A Coulomb failure stress transfer model produced by the first event along optimally-oriented planes allows identifying the areas with positive stress loads where the rupture of the subsequent aftershocks may have occurred. The positive ∆ CFS areas are compared for two depth intervals: 3-10 km and 15-22 km overlapping over 350 relocated hypocenters, giving arguments supporting the interpretation of ∆ CFS as a main mechanism for aftershock triggering in deeper zones of the upper crust.