The safety of complex Socio-Technical Systems highly depends on the non-linear interaction of variabilities between task performances in human, machines and working environments and proper management of those is essential to ensure the safety. However, the practical means to ensure the safety of those systems have not been established yet, and this is mainly due to the gap existing between the theory and the reality as well as to the lack of means for visualizing the potential risks. In this paper, we propose an extended method of FRAM: Functional Resonance Analysis Method and construct a simulator that enables to visualize the potential risks. Then, an example of interactive analysis using the simulator is presented, which enables us to visualize the degrees of resilience of an existing work procedure in operation in facing with potential variabilities. In the end, how to utilize the proposed method for the establishment of the resilient systems from the point of view of the design of operation procedures is presented.