Influence of Soil Conditions on Building Damage Potential during Earthquakes

On the basis of the ground motions recorded in San Francisco during the 1957 earthquake, it is shown that ground motion characteristics varied markedly along a 3-mile section of the city, depending on the variation in soil conditions. It is suggested that building damage potential during earthquakes depends on either the induced/design lateral force ratio or the damage potential index and variations in these quantities are shown, both for the 1957 earthquake and for other earthquakes that may affect the city. Variations in soil conditions are shown to cause the response of structures to vary by factors ranging from 3 to 6, and the types of soil conditions causing maximum response in different types of earthquakes are discussed. It is suggested that building codes should reflect the potential variations in damage potential due to local variations in soil conditions by appropriate variations in design requirements.