Preliminary Geological Site Condition Map of Korea
The average shear wave velocity in the upper 30 m defined from borehole data is routinely used for classifying the site conditions. However, nation-wide information of site conditions is not available in Korea because it is difficult to classify the site condition using the limited borehole data. Also, it requires considerable financial investment and time to acquire and to analyze the necessary geological and geotechnical data obtained from borehole data. Hazards and risk assessments are known to highly dependent on geologic site conditions. Therefore, it is desirable to explore alternative methods to provide the general site conditions on a regional scale. Fortunately, comprehensive information of geologic units and geomorphology of Korean Peninsula is available in digital maps for GIS users. We used geologic units and rock type information from the geologic map, and slope and elevation information from the geomorphologic data to classify the sites. The results reveal Class B sites (mainly rock) are predominant, although softer sediments at sites located near rivers or on landfills are often found. We compared our results to the borehole data which includes locations and ground conditions. There are some differences between the results. The discrepancy is attributed to the relatively large scale geologic map (1:250000) which may not include accurate site condition of the regions. These results provide useful information for the further study of regional hazard estimation, risk management, and other seismological and geotechnical applications or land use planning in developing areas.