We perform numerical experiments by using a mass–spring fault model subject to an external coseismic stress perturbation due to a remote seismic event happening on another fault, the causative fault. In particular, the aim of this study is to investigate the instantaneous fault interaction and possible triggering that happens when a fault perturbed by a stress change fails before the so–called unperturbed instability. As a realistic example we focus our attention on the instantaneous dynamic triggering phenomena occurred during the 17 June 2000 south Iceland seismic sequence in the South Iceland Seismic Zone (SISZ, Reykjanes Peninsula). The main event (Ms 6.6) was followed by three large events within a few tens of seconds (8, 26 and 30 s, respectively) located in a neighborhood of...