# Geo-Proxy-Based Site Classification for Regional Zonation of Seismic Site Effects in South Korea
## 5 Conclusions  
In this study, geo-proxy-based site classification was proposed based on empirical correlations with site response parameters and conducted for regional zonation of seismic site effects to identify the amplification of characteristics in South Korea depending on the site-specific geo-spatial conditions. In order to optimize the classification criteria, by considering the geotechnical uncertainty and site effects in South Korea, a dual framework for a site classification system with site response parameters and geo-proxies was established. First, a geotechnical DB was constructed from borehole datasets, DEM and a geographic coverage map. This study selected the western metropolitan areas (the Seoul and Incheon regions) in South Korea, where reliable geotechnical datasets and land coverage information were spatially distributed well. Second, geo-spatial grid information, which included geotechnical layers, SPT-\(N\) value and DEM, was determined based on the optimized geostatistical interpolation method. The geo-spatial grid information in the Seoul area was applied as backbone datasets to develop the seismic zonation with seismic response parameters based on the validated classification system and the correlations between seismic response parameters and DEM were normalized to develop the geo-proxy criteria. Based on the geotechnical information calculated for these grid locations, various site effect parameters (\(H\), \(V_{S30}\), \(V_{S,soil}\), \(T_{G}\), \(V_{S}D_{S}\)) and geo-proxies were rearranged or calculated. Third, depth to bedrock, \(V_{S30}\) and site period were computed using the thickness of the geotechnical layer with representative \(V_{S}\) for each layer based on the verified criteria for seismic site classification. The empirical method for an efficient site classification system based on the site period, which can reasonably represent the site-specific geotechnical characteristics of Seoul, was derived. The site classification B, in which ground motion amplification does not occur, was dominant. However, plain land adjacent to the Han River and its tributaries was found to have site classifications C and D with large ground motion amplification. Fourth, the proposed geo-proxy-based site classification system based on the topographic elevation and slope was applied to the comprehensive area of Incheon. A comparison with site classification precise zoning information through the geo-spatial grid-based development of geo-spatial grid information was performed. To determine the amplification characteristics and cross-check these with the proxy-based criteria, which depended on the site classification system based on the site response parameters, seismic zonation was performed. The site classifications C4, D1 and D2, which have an average slope of 0.006 m/m, were concentrically distributed in plain areas. The site-specific site effects were estimated based on the topographic elevation and were relatively overestimated when topographic effects were not considered. When developing the seismic zonation with the detailed site classification in the plain areas considering topographic effects, the slope-based  
Figure 12: 3D view of seismic zonation with administrative sub-units by computing the average \(T_{G}\) and the proposed geo-proxy for each unit in the study area of Incheon: (**a**) \(T_{G}\); (**b**) slope (proposed criterion). site classification was more suitable for Incheon. Therefore, the spatial distribution of site class with the slope-based proxy was utilized for developing the seismic zonation. Geo-proxy-based seismic zonation could be a useful tool for disaster response planning and could provide important information regarding the potential condition and recovery times of crucial lifelines, such as roads, rail networks and ports [17; 34]. Although studies on site classification systems are still being conducted, their comprehensive analysis and quantification must be conducted.