## 4 Multilayered Local Zonation of Seismic Site Effects
### Multilayered Local Zonation  
The seismic zonation (Figure 10) of multivariate site response parameters (\(V_{S30}\), \(T_{G}\), \(H\), and \(V_{S,Soil}\)) was developed based on the multiscale grid information assigned to each geo-layer thickness and average \(N_{60}^{exp}\). The \(V_{S30}\) ranged from approximately 340 m/s to 520 m/s in urban areas (i.e., buildings in Figure 1e) with dense residential and industrial facilities. The \(T_{G}\) was widely distributed and varied from approximately 0.2 to 0.5 s in most flat areas adjacent to the urban area. Considering the possibility of structure resonance, urban facilities between 2 and 5 stories high, which are 37% of masonry buildings, 29% of reinforced concrete buildings, and 19% of steel buildings, 15% of the other buildings (Figure 1e), would be vulnerable, assuming that the natural period of building floor is 0.1 s [21,67]. The influence of seismic fragility depends on the type of buildings and construction material is not considered. Accordingly, the seismic fragility function of the damaged buildings can be derived by computational simulation and contrasted with the severity of the exposure to damage. The \(H\) was deeply distributed over 20 m, mainly in central urban areas, except for the mountainous and hilly areas (below 10 m). The D2-E was classified at the central and northern basins with Quaternary alluvium regions less than 10 m in elevation; the slope was \(5^{\circ}\). \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Site Class**} & \multirow{2}{*}{**Site Description**} & \multicolumn{2}{c}{**Parameters for Classification**} \\ \cline{3-4}  & & **Bedrock 1 Depth, \(H\) (m)** & \(V_{S,Soil}\) (m/s) \\ \hline \(S_{1}\) & Rock & \(H<1\) & - \\ \hline \(S_{2}\) & Shallow and stiff soil & \(1\leq H\leq 20\) & \(\geq\)260 m/s \\ \(S_{3}\) & Shallow and soft soil & \(1\leq H\leq 20\) & \(<\)260 m/s \\ \hline \(S_{4}\) & Deep and stiff soil & \(20<H\) & \(\geq\)180 m/s \\ \(S_{5}\) & Deep and soft soil & \(20<H\) & \(<\)180 m/s \\ \hline \(S_{6}\) & \multicolumn{2}{c}{Special soil requiring site-specific evaluation} \\ \hline \hline \end{tabular} 1  
\end{table} 
Table 2: Seismic site classification system of MPSS 2017 [64]. Based on the spatial distribution of site response parameters, site classification criteria C (C1 to C4) and D (D1 to D4), which correspond to vulnerable site conditions, were distributed in the plains near rivers where residential or commercial facilities are concentrated or where industrial facilities are located. In some regions, if the classification according to \(V_{S30}\) is applied, the site classification ranges up to class E. In mountain areas and farmland, most sites classified using the revised seismic design criteria [64] were class \(S_{2}\) or \(S_{3}\), excluding urban areas that were classified as \(S_{4}\) or \(S_{5}\). Seismic zoning plans using the site classification based on \(V_{S,Sail}\) for domestic applications, or \(V_{S30}\) for global standards, are more appropriate with other site parameters to support conservative seismic decision-making processes in a metropolitan area, given that deeper soft ground can better be classified in the same grid unit. In addition, considering that a target area may not only be a residential area, but also an industrial and commercial center, it may be necessary to undertake seismic performance evaluations for large facilities. However, the slight differences in site response parameters adjacent to the threshold that divides the B, C, and D classes, may cause local deviation of a site class in a narrow urban region. If only a single zonation map is used (Figure 10), drastic spatial distortion of the site classification may result. Figure 10: Regional site classification of the seismic site effect parameters: (**a**) \(V_{S30}\); (**b**) \(T_{G}\); (**c**) \(H\); and (**d**) the combination of \(V_{S,Sail}\) and \(H\) based on MPSS 2017. \(V_{S30}\), \(T_{G}\), and \(H\) were categorized by [PERSON] et al. [55].