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GEOSymmc CoIYsuvrAm S <br />Dr. Hari Sharma, P.E., G.E. <br />22 January 2001 <br />Page 6 <br />to "fill" the envelope between the median and 84`h percentile response spectra in the <br />period range from approximately 0.08 seconds to 2 seconds, all three accelerograms <br />were scaled up. In particular, to represent the M,r 6.4 WE, the accelerograms were <br />scaled to a PHGA of 0.13 g rather than a median MPE PHGA of 0.09 g. To represent <br />the M,v 6.7 MCE, the accelerograms were scaled to a PHGA of 0.19 g rather than a <br />median MCE PHGA of 0.13 g. The acceleration response spectra of the time histories <br />selected to represent the M,w 6.7 MCE event on the Great Valley blind thrust system are <br />plotted in Figure 2. The acceleration response spectra of the time histories selected to <br />represent the M,a 6.4 MPE event on the Great Valley blind thrust system are plotted in <br />Figure 3. <br />The magnitude 8+ synthetic accelerogram was selected to represent the MW <br />7.9 MPE/MCE event on the San Andreas fault. To compensate for a duration <br />deficiency and to "fill' the envelope between the median and 84`h percentile response <br />spectra in the period range from approximately 0.08 seconds to 2 seconds, the <br />Magnitude 8+ synthetic accelerogram was scaled to a PHGA of 0.10 g rather than the <br />median MPE PHGA of 0.06 g. The acceleration response spectrum of the Magnitude 8+ <br />synthetic accelerogram representing the MPE/MCE M, 7.9 event on the San Andreas <br />fault system is plotted in Figure 4. <br />This letter report presents a seismic site exposure evaluation for the Forward <br />Landfill in San Joaquin County, California. In performing this evaluation, seismic <br />sources capable of generating strong ground motions at the site were evaluated based <br />upon the best available information on regional seismicity and seismic geology. The <br />Maximum Credible Earthquake (MCE) and Maximum Probable Earthquake (MPE) <br />moment magnitudes and site -to -source distance pairs for each of these seismic sources <br />were established on the basis of published data. The Peak Horizontal Ground <br />Acceleration (PHGA) and significant duration of strong ground shaking A) at a <br />hypothetical bedrock outcrop at the geometric center of the site was established for each <br />P:iPWICAWPWM CALIF-WOFORWARDIFOR-HAZDOC <br />0A <br />• <br />