National and Local Geological Seismic Risk Screen

i. Seismic Hazard Screen-See national map (FEMA 154)

ii. Soil Site Clasification

FEMA 310 [replacement of FEMA 178] and FEMA 368 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, 2000 Edition define the following [abbreviated version soil classifications - full descriptions in FEMA 310 Section 3.5.2.3.1 and in FEMA 368 Section 4.1.2.1].  Seismic hazard due to ground shaking can be estimated by analyzing the location of the building with respect to causative faults, the regional and site-specific geologic characteristics, and a selected Earthquake Hazard Level.  However, other seismic hazards could exist at the building site that could damage the building regardless of its ability to resist ground shaking. These hazards include fault rupture, liquefaction or other shaking-induced soil failures, landslides, and inundation from offsite effects such as dam failure or tsunami.

• Site class A - Hard rock with measured shear wave velocity greater than 5,000 ft/sec.

• Site class B - Rock with shear wave velocity between 2,500 and 5,000 ft/sec

• Site class C - Very dense soil or soft rock [velocity between 1,200 and 2,500 ft/sec]

• Site class D - Stiff soil [velocity between 600 and 1,200 ft/sec]

• Site class E - Soil profile with velocity less than 600 ft/sec

• Site class F - Soils require site-specific evaluations [liquefiable, peats, high plasticity, or very thick soft/medium clays.