The 2008 U.S. National Seismic Hazard Map Applications for Building Codes
PETERSEN, M., U.S. Geological Survey, Golden, CO USA, firstname.lastname@example.org; HARMSEN, S., U.S. Geological Survey, Golden, CO USA, email@example.com; RUKSTALES, K., U.S. Geological Survey, Golden, CO USA, firstname.lastname@example.org; LUCO, N., U.S. Geological Survey, Golden, CO USA, email@example.com
The 2008 U.S. National Seismic Hazard maps incorporated several new models and datasets including: new and revised fault source models; NGA, CEUS, and subduction-interface ground-motion prediction models, updated seismicity catalogs and estimates of uncertainties; UCERF 2.0 model for California; and recommendations from WSSPC on the Intermountain West. Ground shaking changed by 30 % at several sites across the conterminous U.S. The hazard maps have been adopted as the basis for building code maps in the 2009 NEHRP Recommended Provisions, 2010 ASCE Standard, and 2012 IBC. For the building code maps we also developed deterministic median hazard maps that are used to limit the design ground motions over some active faults. These maps were prepared using the same weighted ground motion prediction equations and mean characteristic earthquake magnitudes that were applied in the probabilistic maps. We are now considering the next update of the maps that will be due in 2013-2014. We will hold a user workshop in 2012 or 2013 to discuss products that would be helpful for the engineering community in mitigating earthquake risk. Some of the issues that may be considered include: (1) Spectral periods in design codes - Should a series of maps ranging from 0.1 s to 5.0 s spectral accelerations be used directly in building codes? (2) Soils maps– Which Vs30 maps should be developed and how can we translate ground-motion prediction equations to appropriate Vs30 levels? How do these soil maps compare with amplifying the 760 m/s maps using the NEHRP factors? (3) Directivity – How should directivity be incorporated into maps? (4) Time dependence – Should renewal or clustering recurrence models be incorporated in hazard maps? (5) Ground-motion parameter – Should we make maps for maximum component ground, that are applied in the building codes, as well as geometric mean ground motions?