Latest harmful earthquakes showed that earthquake-induced geotechnical hazard and corresponding structural disasters are usually even worse over soft soils than over firm soils or rocks in urban areas. That is, the local geologic and soil conditions include a profound effects on the amplification of earthquake ground motions, which may lead to the serious seismic hazards. The difference of seismic amplification potential between the sites in a region would be estimated by spatially predicting the subsurface soil thickness and the corresponding seismic response behavior in the entire area of interest. In the spatial prediction of the subsurface geotechnical conditions across the area of interest, in-situ site investigation data in and near the area can be efficiently used as the basic resources and geotechnical expert knowledge can be also applied for enhancing the prediction reliability.