NEHRPSiteClassesTetonCountyIdaho

National Earthquake Hazard Reduction Program (NEHRP) seismic site classes for Teton County, Idaho are contained in this shapefile. The intensity of ground shaking during an earthquake varies according to the nature of near-surface materials. NEHRP site classes quantify this effect and permit adjustment of expected ground motion. The site classes were determined in two ways. In the detailed study area containing populated parts of the county, i.e. the towns of Driggs, Victor, and Tetonia, 31 Vs30 measurements were made by Fugro Consultants Inc. using the IMASW technique (O'Connell and Turner, 2011). These measurements were interpolated within the detailed study area using geologic and geomorphic criteria to produce a map. The map contains six classes: C3 (760-620 m/s), C2 (620-490 m/s), C1 (490-360 m/s), D3 (360-300 m/s), D2, (300-240 m/s), and D1 (240-180 m/s). Vs30 measurements ranged between 217 m/s and 734 m/s . Outside of the detailed study area,  Vs30 was estimated using the U.S. Geological Survey's Global Vs30 Map Server (available at http://earthquake.usgs.gov/hazards/apps/vs30/). This technique uses topography as a proxy for Vs30. It produces a map with the same six classes as in the detailed study area. The two maps do not agree in many places along their boundaries. In areas with low relief, the Global Vs30 mapper method generally underestimates Vs30 compared to Vs30 measurements.

Provides preliminary NEHRP site classes for Teton County, Idaho.

Report and Appendices included with this dataset on IGS website
FUGRO CONSULTANTS INC. 
Appendix A: Inversion Results
Appendix B: Final Vp-Vs Spreadsheets with Vs30 and Vs50 Calculations
Appendix C: Correlation Green's Function Waveforms
Appendix D: IMASW Calibration Certificate

Polgyon positions showing NEHRP site classes are approximate and may not reflect true site conditions. This map is designed for use at 1:50,000 and is not suitable for engineering-scale work. The position of polygons showing NEHRP site classes is derived in two ways: 1) within detailed study area corresponding to populated area of coutny, Vs30 measured at 31 locations in populated area of county and interpolated to rest of study area with geologic/geomorphic criteria. Polygon locations are approximate except in immediate vicinity of measurement sites; 2) in remainder of county, polygons determined with USGS Vs30 Global mapper application. This application uses topography as a proxy for Vs30. The grid size for Vs30 Global mapper is ~2000  x 3000 ft (610 x 914 m).