Recently produced earthquake hazard maps with geologic emphasis, including one for the greater St. Louis area at a scale of 1:100,000, focus on broad scale geologic properties that indicate hazard, e.g., likelihood for liquefaction and or landslide. Hazard assessment requires knowledge of how local geological properties affect expected ground motions. This can be done by defining generic soil property profiles in the state and using them in computer models to predict local effects. Classification of earthen materials to identify shaking susceptibility could utilize a standard Central United States Earthquake Consortium (CUSEC) descriptive format.
The professional community has powerful procedures for evaluating potential ground motion at a site. Such investigations are expensive for siting, planning and preliminary design, because extensive site information resulting from borings, soil testing and geophysical investigation is required. On the other hand, development of generalized soil profiles would quantitatively assist in hazard assessment when combined with the geologic hazard mapping and expected ground motion overlays.
Create generalized soil models for specific counties or hazard maps. Generalized soil profiles would allow design software to initially assess sites before the expense of the necessary field testing and structural design phase. The resulting initial guidance would clarify the economic considerations for planning, site selection and development. Generalized soil profiles could be augmented with site specific data to refine ground shaking parameters for evaluation of existing or future structures. Knowledge of local site conditions permits realistic assessment of damage potential of existing structures.
Several resources would be brought together to develop generalized soil models. The DGLS has the professional capability to define the generalized soil profiles. State agencies, consulting firms and professional societies possess soil and rock information and Federal agencies have data bases of soil and rock properties, including shear wave velocities. A programmatic approach to soil profiles should be developed for their use with either 1:100,000 or 1:24,000 scale hazard mapping.