Geostatistical assessment for the regional zonation of seismic site effects in a coastal urban area using a GIS framework

Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by local geologic conditions such as soil thickness, bedrock depth, and soil stiffness. Seismic disasters are often more severe over soft soils than over stiff soils or rocks due to differences in local site effects. In this study, on the basis of a geotechnical information system (GTIS) framework, we developed an advanced geostatistical assessment for the regional zonation of seismic site effects. In particular, to reliably predict spatial geotechnical information, we developed a procedural methodology for building an advanced GTIS within a geographic information system framework and applied it to the Busan area in Korea. The systemized GTIS comprised four functional components: database, geostatistical analysis, geotechnical analysis, and visualization. First, to build the GTIS, we collected pre-existing geotechnical data in and around the study area, and then conducted a walk-over site survey to acquire surface geo-knowledge data. Second, we determined the optimum geostatistical estimation method using a cross-validation-based verification test, considering site conditions. The advanced GTIS was used in a practical application to estimate the site effects in the study area. We created seismic zoning maps of geotechnical earthquake parameters, such as the depth to bedrock and the site period, and present them as part of a regional synthetic strategy for earthquake risk assessment.