Studying the influence of the earthquake on different structures interacting with soil has become a priority, due to the devastating damage caused by the earthquake on these types of constructions. In this book, the effects of the dynamic load on earth retaining walls have been studied. In particular, the aim of this study is to develop fragility curves for these structures. They describe the probability of a structure being damaged beyond a specific damage state for several levels of ground shaking. In this respect, several numerical models were built to carry out advanced numerical simulations by using a plain strain commercial software FLAC (Fast Lagrangian Analysis of Continua), based on the finite difference method. Models of wall used in analyses are trapezoid shape gravity earth retaining wall with different height. For each wall two main configurations of backfill have been used: in the first one, the surface of backfill is horizontal while in the second one the backfill is inclined of 30°. The geometry of each wall satisfies the safety static condition according to the Italian Technical Code prescription.