GIS-based regional assessment of seismic site effects considering the spatial uncertainty of site-specific geotechnical characteristics in coastal and inland urban areas

Abstract

Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by site-specific geologic conditions such as soil thickness, bedrock depth and soil stiffness. Seismic disasters are often more severe in coastal or riverside locations than over stiff soils or rocks due to differences in local site effects. In this study, a recently developed geographic information system-based framework was applied in coastal and inland urban areas in Korea, and its applicability for regional assessments was evaluated using appropriate geostatistical zonation of site-specific seismic site effects. The proposed framework was composed of four functional components: multivariable statistical clustering, geostatistical optimization, geotechnical analysis, and local visualization. The framework was applied in the Seoul and Busan areas of Korea for consideration of site effects in inland and coastal urban areas. Such zones of thick soil, or with a deep depth to bedrock, are susceptible to ground motion amplification due to site effects during earthquakes. The earthquake losses associated with possible building damage can be estimated based on spatial zoning maps considering geological and topographical characteristics and by a comparison of the spatial correlations of seismic site classes between inland and coastal areas of Korea.

Geo-Proxy-Based Site Classification for Regional Zonation of Seismic Site Effects in South Korea

“…In addition to the existing V S30 , various site response parameters are examined and identified, including T G , V S Ds (D S < 30 m) and V S,soil [4,6,18]. T G and V S,soil can be calculated by Equations (2) and (3), respectively.…”

“…Sun [2,4] and Sun and Kim [18,24] conducted seismic response analysis for various site conditions in South Korea, analyzed the results and recalculated domestic site coefficients to systematically reflect the site-specific seismic response characteristics in South Korea. In addition, their studies suggested various improvement measures for the domestic geotechnical classification system and the subdivision of the geotechnical classification.…”

“…In particular, the geostatistical optimization of the interpolation method and clustering estimation was developed as a computational framework to construct the appropriate seismic zonation using a geo-spatial DB, which was composed of multi-variable geo-data [18]. Accordingly, the typical geotechnical layer information, which was categorized into fill, alluvial soil and weathered layer, was constructed as a spatial distribution map separated into 100 m mesh areas.…”

“…Sci. 2018, 7, x FOR PEER REVIEW 3 of 23 geo-spatial DB, which was composed of multi-variable geo-data [18]. Accordingly, the typical geotechnical layer information, which was categorized into fill, alluvial soil and weathered layer, was constructed as a spatial distribution map separated into 100 m mesh areas.…”

“…In order to estimate the site-specific site effects, empirical correlations among geotechnical layers, SPT-N value and V S have been proposed using the borehole datasets in partial metropolitan areas based on appropriate statistical regressions. Accordingly, a seismic zonation map with site response parameters, according to the Korean seismic codes, was developed by considering correlations between the spatially interpolated borehole information [18]. The site effects, resulting in the amplification of earthquake ground motion, are strongly influenced not only by the subsurface soil conditions and structure but also by the surface topography.…”