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Foothill Sanitary Landfill – Seismic Characterization 5 03.18.2015 <br />4.0 Gr o u n d Mo t i o n s <br />Horizontal ground motions (peak ground accelerations [PGA]) were estimated for each of the <br />seven seismic sources noted in the previous section based on information obtained from the <br />USGS (2008) Faults Source Parameters website. Estimations of the ground motions resulting <br />from the MCE event on each seismic source were made using the 2008 and 2014 NGA empirical <br />attenuation models developed by Abrahamson and Silva. Were To perform the ground <br />attenuation modeling, the following fault characteristics were required in the model: <br />ƒDip - the average dip of rupture plane (degrees); <br />ƒMw - MCE maximum moment magnitude; <br />ƒRJB - the closest distance to the fault surface projection (km); <br />ƒRRUP - the closest distance to the coseismic rupture (km); <br />ƒRX - the horizontal distance to the top of the fault rupture (km); <br />ƒVS30 - the average shear wave velocity over a subsurface depth of 30m (m/s); <br />ƒW - the fault rupture width or distance to rupture bottom (km); <br />ƒZTOR - the depth to top of the coseismic rupture (km); <br />ƒZ1.0 - the depth (km) to VS = 1 km/sec; and <br />ƒZ2.5 - the depth (km) to VS = 2.5 km/sec. <br />Additionally, depths to shear wave velocity horizons are required for the modeling, and an <br />estimated average shear wave velocity of 455 m/s in the upper 30 m of the site was used in the <br />modeling based on the 1:24,000 scale Geologic Map of the Sacramento Quadrangle, which <br />shows that the site is underlain by Quaternary to Tertiary (Pleistocene-Pliocene) alluvial deposits <br />(Wagner, Jenning, Bedrossian, and Bortugno, 1981). Table 20 in the California Geological <br />Survey (CGS) Report No. 222: HAZUS Scenario and Annualized Earthquake Loss Estimation of <br />California assigns a Vs30 of 455 m/s to this rock type (Chen, Branum, and Wills, 2011). Figure <br />2 and Figure 3 illustrate how the Vs30 of 455 m/s was determined. <br />The MCE ground motion results (PGA) from the 2008 and 2014 NGA attenuation models are <br />summarized in Table 2 on the following page. Also presented on Table 2 are the results of the <br />previous seismic characterization results for comparative purposes. The NGA attenuation results <br />are presented in Attachment 2.