EGL Ref: 8983 8 October 2021 Page 17 File: TSF3 Stability Analysis Appendix Summary.docx.doc and then at approximately 1.1 to 1.3 s it is approximately 3 to 3.5s. The highest spectral amplification likely corresponds with the embankments natural period of resonance and while this amplification was recorded the natural period of any slide masses at the crest would have been much lower and so not experience notable amplification effects. Recorded events indicate higher amplification ratios for lower shaking intensities where embankment materials are closer to their elastic range and hysteretic damping is lower, and lower amplification rations for higher shaking intensities where embankment materials are further into their non-linear range with greater hysteretic damping. The peak ground accelerations for each of the seismic case are listed below: • 150-year return period earthquake: PGA = 0.10g • Kerepehi F.S. Rupture 84%ile PGA = 0.23g • Kerepehi aftershock 84%ile PGA = 0.16g • 10,000-year return period earthquake: PGA = 0.39g • 10,000 year aftershock: PGA = 0.23g The selected amplification ratios are: • 150-year return period earthquake: AMP = 3.6 • Kerepehi F.S. Rupture 84%ile AMP = 2.0 • Kerepehi aftershock 84%ile AMP = 2.7 • 10,000-year return period earthquake: AMP = 1.5 • 10,000 year aftershock: AMP = 2.0 The amplification ratios for ground motions from the base of the embankment to the crest selected are indicatively shown on Figure B11 and Figure B12. FIGURE B11: HARDER (1998) (REF. 7) RECORD OF CREST AND BASE PEAK GROUND ACCELERATIONS Storage 1A Amplification Factors
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