4.1. Stress transfer from the creeping segment of NTF to AVD
The stress tensor produced by the defined slip model for the creeping segment of NTF is calculated on a 3-D grid in the region using a method by Wang et al. (2003) (Fig. 3). The method is based on the dislocation theory that is implemented in a multilayered media. A 1-D crustal velocity model of the area retrieved from precisely located aftershocks of AVD is used, and a Poisson ratio of ∼0.25 obtained from a Vp/Vs ratio of 1.74 (Momeni & Tatar 2018, Table S1). The Coulomb stress field is calculated on optimally oriented ruptures of both Ahar-Varzaghan earthquakes, and by considering strike-slip mechanisms of their slip patches obtained by Momeni et al., (2019).
A positive Coulomb stress of >1 bar is transferred from the creeping segment on the ruptured areas during the doublet (Fig. 3a). Also, the creeping segment had positive coulomb stress transfer of >4 bar on the nearby segments and excited them to slip (Fig. 3b), especially on the western segment of NTF (e.g., Vadacca, 2020).