The underappreciated significance of perpendicular-to-facing relative settlements of geosynthetic reinforced soil (GRS) walls in seismic analyses is evident in the current literature, particularly when compared to along-facing settlements. Consequently, this study conducted a series of seismic finite element analyses to evaluate the perpendicular-to-facing settlements of a 20 m GRS wall during 36 significant worldwide earthquakes. Static and dynamic verifications of numerical modeling were performed by comparing the results of a 3.6 m physical GRS wall model and a 1 m shaking table test at the Royal Military College (RMC) of Canada, respectively. The reinforced soil modeling utilized the hardening soil constitutive model with small strain stiffness (HS-small). Additionally, the facing of the GRS wall model comprised 0.5 m × 1.5 m concrete panels. The findings emphasized the critical nature of relative deformations between the facing and reinforced zones, and between the reinforced and retained zones, in addition to absolute settlements. Moreover, the amount of relative settlements was found to be correlated with the intensity of seismic excitations. The correlations between relative settlements and intensity of earthquakes were also proposed based on the results of the current research.