Effects of DEM Resolutions for Site Classification in Southeastern Korea

Site characteristic is an important input parameter in the hazard assessments of earthquakes, liquefactions, landslides and other natural disasters. We prepared a preliminary site classification map using the geologic and topographic maps of Korea in the previous study, in which slope and elevation data derived from digital elevation model (DEM) were used as important indicators to infer the shear wave velocity in the upper 30 m (Vs30). We may use DEMs in different resolution, which may influence the results of the site classification. In order to explore the effects of different DEM resolutions, three DEMs in 3, 9, and 30 arc-seconds are used to develop and to compare independent site classification maps of southeastern Korea. We observed the largest difference (approximately 5%) in site C classified by the slope criteria using 9 and 30 arc-sec DEMs. We also found variations as large as 3% in site B and E. In the area where large variation of slope occurs, for example mountainous region with occasional flat topography, high resolution DEM can detect variations over short distance. However, site classification map developed using a low resolution DEM is characterized by smoother variations in topography, thus results in averaged site classes. We also note only minor differences (less than 0.7%) in the elevation-based site classification maps using three different DEMs. Apparently, it is suitable to use a higher resolution DEM to represent the rugged topography in southeastern Korea. Finally, the site classification using higher resolution DEM will provide useful information in the study of regional hazard estimation and risk management.