PRELIMINARY NEHRP SITE CLASSIFICATION AND SOIL AMPLIFICATION MAP OF OKLAHOMA

The preliminary goal of this work is to generate a state-wide National Earthquake Hazards Reduction Program (NEHRP) site classification based on published Oklahoma Geological Survey (OGS) geologic maps and the Soils Map of Oklahoma. Sites are classified according to the NEHRP soil classification scheme, which are categorized from inferred shear wave velocities (Vs) and their relationship to potential amplification of ground shaking (A, B, C, D, E, and F) during an earthquake. Areas labeled F are dominated by soils vulnerable to possible failure or collapse under seismic loading and include liquefiable soils, quick and highly sensitive clays, and weakly cemented soils. These soils are mostly saturated or partially saturated sand in Quaternary alluvium. This map represents a first step in understanding the distribution of earthquake hazard potential in Oklahoma based on assumed soil properties. Further mapping and site-specific measurements should be conducted in order to better understand the physical characteristics of the soils and their potential for amplification of earthquake-induced ground motions.