The lining structure of Tunnel Boring Machine (TBM) excavated tunnels is composed of a series of precast Reinforced Concrete (RC) pieces called segments. In this paper, a novel method is introduced for seismic retrofitting of segmental tunnels located in active fault zones in rock environment, on a case study of the Amirkabir dam-Tehran water Transfer Tunnel (Karaj Tunnel). The main design concept in this method is based on stiffness degradation of the tunnel structure, intersecting with central fault zone. . Even strong structures do not tolerate the faults displacement, and will ultimately fail. Therefore, the logical solution for stiffness degradation is providing life safety operational limit. Stiffness degradation develops due to the creation of sequential joints in segments intersecting with central fault zone; so, it is called sequential joints method. In this method, a joint is considered between each or multiple rings to synchronize the tunnel structure with the tunnel displacements during the faulting process, and to avoid the global failure of the tunnel structure. This method is currently applied on the second part of the Karaj water transfer tunnel (Part K”-BR).