Coir fiber reinforcement is adopted in many geotechnical applications and has been found very effective in improving the static characteristics of soil. However, the stability of soil is crucial when it is exposed to various dynamic loading conditions. In geotechnical practices, dynamic analyses are used to assess and reduce the risk of potential earthquake hazards by evaluating the response of structures subjected to dynamic stresses. Foundation isolation of structures involves reducing the magnitude of dynamic loads transmitted during seismic events. In the present study, coir fiber-reinforced soil has been applied under the foundation bed. A three-dimensional finite element model was developed using ABAQUS 2018 software to analyze the variation of thickness of the coir fiber reinforced soil bed when compared with the unreinforced soil layer. Three earthquakes, i.e., the 2015 Nepal earthquake, the 2016 Manipur earthquake, and the 2021 Assam earthquake, were considered for the study. The soil reinforced with 1.0% coir fiber exhibited a higher energy absorption potential than unreinforced soil, which would reduce the intensity of seismic stresses exerted on the structure. The results obtained from the numerical analysis suggest that the fiber reinforcement of soil below the concrete foundation bed leads to a reduction in the displacement of the foundation structure when subjected to earthquake load.