SOIL AMPLIFICATION MAPS FOR ESTIMATING EARTHQUAKE GROUND MOTIONS IN THE CENTRAL US

The Central United States Earthquake Consortium (CUSEC) State Geologists are developing soil amplification maps to assist state and local emergency managers and community officials in evaluating the earthquake hazards in the 7 CUSEC States. The geological surveys of the states surrounding the New Madrid and Wabash Valley Seismic Zones have used a consistent classification of soils for amplification characteristics to map the seismic shaking potential in the eleven 1- x 2-degree (scale 1:250,000 or 1 inch=3.9 miles) quadrangles that cover the high risk areas of these seismic zones. Currently, 1:24,000 scale (1 inch=2,000 feet) soil amplification maps covering Cape Girardeau, Missouri; Evansville, Indiana and Carbondale, Illinois and their surrounding areas have been completed and other areas are actively being mapped at this scale. Shear wave velocities for surficial materials are measured and used to classify the soils according to how much they may amplify earthquake ground motions. Geologic base maps of surficial materials or 3-dimensional materials maps, either previously existing or produced for this project, are used in conjunction with the shear wave velocities to classify the soils for the upper 15 to 30 meters. These maps, produced in an electronic form suitable for inclusion in the Federal Emergency Management Agency's Earthquake Loss Estimation Program (HAZUS) replace the default information of one soil type for the entire Midwest with six soil types consistently classified throughout the region. The HAZUS program used with detailed soil amplification maps can generate realistic earthquake scenarios for use in developing earthquake emergency response and recovery plans, conducting training exercises and making land use decisions. The various scale soil amplification maps can be used in scenarios and planning that cover multi-state, to county and city level regions to improve public safety.