Laserfiche WebLink
603284-001 <br />APPENDIX D <br />Site-Specific Ground Motion Study <br />Background <br />Leighton performed a site-specific ground motion study in accordance with the <br />requirements of the 2010 California Building Code. A Probabilistic Seismic Hazard <br />Analysis (PSHA) and Deterministic Seismic Hazard Analysis (DSHA) were performed <br />concurrently to evaluate the likelihood of future earthquake ground motions at the <br />project site. The PSHA and DSHA incorporate the average results of three different <br />Next Generation Attenuation (NGA) relationships by Boore and Atkinson (2008), <br />Campbell and Bozorgnia (2008) and Chiou and Youngs (2007). The site coordinates <br />used in this analysis are N 33.76184° and W 1 17.90095°. The site is classified as Site <br />Class F based on potential for liquefaction of the onsite soils. Shear wave velocity was <br />measured using cone penetration test from the subsurface explorations performed by <br />Leighton. <br />Design Criteria <br />The level of earthquake ground motion criteria considered for the PSHA corresponds to <br />the probabilistic maximum considered earthquake (MCE), defined as an earthquake <br />event having a 2 percent probability of being exceeded in 50 years, using the spectral <br />response acceleration 5 percent damped of the ground motion.This event is <br />approximately equivalent to the 2,475-year average return period earthquake. <br />The level of earthquake ground motion criteria considered for the DSHA corresponds to <br />the deterministic MCE, defined as the 150 percent of the largest median 5 percent <br />damped spectral response acceleration of the ground motion at each spectral period of <br />all sources analyzed. The deterministic MCE was checked against the lower limit <br />stipulated in Figure 21.1-1 of ASCE/SEI 7-05. <br />Methodology <br />The 2010 CBC requires the procedures of Chapter 21,Site-Specific Ground Motion <br />Procedures for Seismic Design, of the Minimum Design Loads for Buildings and Other <br />Structures (ASCE/SEI 7-05)published by the American Society of Civil Engineers <br />(ASCE) be used to determine the site-specific seismic design parameters when <br />performing a site-specific ground motion study. We first perform a PSHA and DSHA, <br />then determine the code-specified seismic design parameters, then process them in <br />D-1