Issues on Seismic Site Characterization

Abstract

It has already been well established that geotechnical characteristics of ground have considerable impact on the performance of structures founded on them during earthquakes. The thickness of overburden, number of layers of ground and their individual thickness, properties of soil such as stiffness, strength, and damping characteristics, location of groundwater table, type of input motion at bedrock, type of material, and quality of construction among many are the factors influencing the ground motion at the surface. Soft and less dense soil is likely to experience considerable amplification in ground motion with long period components. On the other hand, stiff soil is likely to experience lesser level of amplification containing more of short period components. There have been situations when a particular type of structure has suffered severe damage during an earthquake whereas some poorly built structures have performed better. There have been a large number of efforts to bring out analytical formulations by researchers in this regard. However, there is still a large variation in the actual behavior and predictions by different models. Further, some complex models suffer from the lack of precise data for arriving at solutions closer to reality. This paper presents some issues with regard to site characterization under seismic environment.