EGL Ref: 8983 8 October 2021 Page 7 File: TSF3 Stability Analysis Appendix Summary.docx.doc EMBANKMENT CO-SEISMIC DEFORMATION CALCULATIONS B4. PURPOSE Estimate the potential co-seismic deviatoric (shear) embankment deformations under earthquake loading for Storage 3 TSF embankment raise to RL155. B5. OBJECTIVES 1. Select design response spectra and mean moment magnitudes (Mw) for the dam site (Vs30 = 600m/s) for an: a. Operational Basis Earthquake - 150 year return period event b. Safety Evaluation Earthquake - 84%ile Shaking Intensity from a rupture on the Kerepehi Fault System and aftershock c. Safety Evaluation Earthquake - 10,000 year return period event and aftershock 2. Estimate the embankment shearwave velocity profile 3. Estimate the amplification factors (base to crest) for embankment spectral response and topographical effects 4. Estimate the ground motion variation through the embankment 5. Estimate the co-seismic deviatoric deformations induced by earthquake shaking using the Bray and Macedo (2019) calculation method B6. DESIGN RESPONSE SPECTRA A seismic hazard study was undertaken by GNS Science in 2017 (Ref. 1) for the Waihi Operation site with a time average shearwave velocity over 30m, Vs30 = 600 m/s, representative of a soft rock site. The GNS study provided probabilistic uniform hazard spectra for the required: • 150 year return period earthquake event • 10,000 year return period earthquake event EGL assessed the spectrum for the aftershock following 10,000 year return period earthquake event. The GNS study (Ref. 1) also assessed the deterministic spectrum for the required 84%ile rupture on the Kerepehi Fault System. EGL assessed the spectrum for the aftershock on the Kerepehi Fault System. 6.1. Operational Basis Earthquake - 150 year return period earthquake event The Operational Basis Earthquake probabilistic 150 year return period uniform hazard spectrum is shown in Figure B1 and the associated deaggregation plots are shown in Figure B2, Figure B3, and Figure B4. The mean magnitude of the deaagregated rupture sources for PGA (Peak Ground Acceleration) is provided by GNS (Ref. 1), however, not for SA(0.5s) and SA(1.0s). These have been visually estimated as summarised in Table B8 by EGL for use in estimating co-seismic displacement.
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