## 5 Discussion  
Discussions were previously presented (Sections 2-4) for each aspect that was considered. What follows is a synthesis of the aspects discussed. MPs have complex behavior that is a function of many factors: type of grouting, MP shape, surrounding soil (in this case mainly soil dynamic properties and stratigraphy), superstructure, MP-to-structure connection, loading, among others. In Section 3.2, a synthesis of these factors of influence is presented, as the authors' point of view and each one is discussed in detail. As far as the MP-related factors are concerned, the studies found in the literature and the authors' analyses showed that the execution technology highly influences the seismic behavior of MPs, especially the grouting method, owing to the modifications that are produced in the surrounding soil, including densification and stiffness increasing, depending on the technology and also some execution details (type of packer, for example). Even if some studies can be found in the literature on these execution aspects, for instance, there is no clear relationship between a certain method and a specific behavior. The geometrical features of MPs, such as the inclination, length, diameter, or spacing, also influence the seismic behavior, being found that the most important are the slenderness (L/d) and the spacing (number). Additionally, the inclination was found to strongly influence the amplification factor, owing to stiffness modification between vertical and inclined MPs, but also the load repartition between MPs and the raft. The modifications that the inclination is leading in terms of dynamic amplification occurs both at the level of MP cap and attached mass, with some differences found when different excitations are applied (harmonic or actual seismic event) and for various types of connection between the MPs and raft. The factors related to the surrounding soil that interacts with MPs are, of course, also important, as the soil influences the propagation of the seismic wave. Therefore, this interaction can affect the seismic input motion; the homogeneity, stiffness, or constitutive model of the soil influence the behavior. It was found that the damping values and the seismic response in general are affected by the heterogeneity of the soil, and a concept of \"filtration\" of the high frequency component of the ground motion was proposed by certain authors. Taking into consideration the drilling and grouting process of MPs, a certain level of heterogeneity can result, which can further influence the seismic behavior through an \"artificial filtration\" or, more precisely, a \"damping out the high frequency components\" of the seismic ground motion. Additionally, the modified soil mass around MPs, forming a sort of MPs-soil block, was found to amplify the seismic waves. Therefore, a conclusion can be drawn, that it is possible to use these MPs as a factor of enhancing the seismic behavior by affecting the wave propagation in the soil. This is one of the aspects not yet studied, but some indirect conclusions could be extracted from the data presented in Section 3.2. These aspects are aimed to be further investigated in the future by the authors of the present paper. MPs are expected to affect the seismic behavior by influencing the mechanism of interaction within the soil-micropile-superstructure system owing to the excitation of seismic waves; this can be enacted by affecting the kinematic and/or inertial interactions. MPs have an important influence on the kinematic interaction, as the embedment depth is relatively high and can cause incoherence in the seismic waves. MPs can also affect the inertial interaction through both stiffness and damping, as was also noted for piles.