3103F.4.2.2 Earthquake Motions From USGS Maps
Earthquake ground motion parameters can be obtained directly from the US Seismic Design Maps tool available at the USGS website (http://earthquake.usgs.gov/designmaps/us/application.php) for the site condition(s) appropriate for the MOT site and the selected probability of exceedance. For this purpose, select the "2013 ASCE 41" as the design code reference document (based on 2008 USGS hazard data available), "Custom" under the Earthquake Hazard Level option, required Probability of Exceedance (in 50 years), and appropriate Site Soil Classification(s) for the MOT site. The USGS tool directly provides the peak ground and spectral accelerations for the selected hazard level and site condition(s).
The alternative method of obtaining earthquake ground motion parameters, from the most current USGS data for selected hazard level and site condition(s), is permitted. If needed, the data for appropriate probability of exceedance may be obtained using the procedure described in Chapter 1 of FEMA 356 [3.1], and corrected for the MOT site as discussed in Section 3103F.4.2.4 or Section 3103F.4.2.5.