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(A)Station:CCCCR rup=2.8 km(B)10 1Station:PRPCR rup=2.5 kmSpectral Acc, Sa (g)(C)Spectral Acc, Sa (g)(E)10 010 -110 -210 0Fault ParallelFault NormalHoriz gmVertPrediction10 -2 10 -1 10 0 10 1Period, T (s)10 -110 -210 1Fault ParallelFault NormalHoriz gmVertPredictionStation:RHSCR rup=6.5 km10 -2 10 -1 10 0 10 1Period, T (s)Station:HVSCR rup=4 kmSpectral Acc, Sa (g)(D)Spectral Acc, Sa (g)(F)10 010 -110 0Fault ParallelFault NormalHoriz gmVertPrediction10 -2 10 -1 10 0 10 1Period, T (s)10 -110 -2Fault ParallelFault NormalHoriz gmVertPredictionStation:CACSR rup=12.8 km10 -2 10 -1 10 0 10 1Period, T (s)Station:LPCCR rup=7.1 kmSpectral Acc, Sa (g)10 010 -1Fault ParallelFault NormalHoriz gmVertPrediction10 -2 10 -1 10 0 10 1Period, T (s)Spectral Acc, Sa (g)10 010 -110 -2Fault ParallelFault NormalHoriz gmVertPrediction10 -2 10 -1 10 0 10 1Period, T (s)▲ ▲ Figure 12. Horizontal and vertical pseudo-acceleration response spectra observed at various near-source strong-motion stations.The prediction shown is for the horizontal geometric mean and dashed lines represent the 16th and 84th percentiles.3.5 seconds, the displacement demands imposed by the groundmotion were in the order of two times the seismic design level.Response Spectra Observed at Various Strong MotionStationsFigure 12 illustrates the horizontal and vertical pseudoaccelerationresponse spectra observed at six locations inChristchurch as well as the empirical prediction for thegeometric mean component of Bradley (2010). No attemptis made here to rigorously assess the adequacy of empiricalground models against the observed near-source groundmotions, and the purpose of the comparisons is simply toillustrate general features of the response at the strong motionstation that depart from that which is nominally expected.Figure 12A illustrates the aforementioned strong long-periodground motion at Christchurch Cathedral College (CCCC)due to basin wave propagation. Figure 12B illustrates the forwarddirectivity polarity in the ground motion at Pages Road(PRPC), with significantly higher long-period ground motionin the fault normal component, as well as a vertical pseudospectralacceleration of 6 g for a vibration period of T = 0.1 s.Figure 12E illustrates that the high-frequency ground motionat Heathcote Valley (HVSC) is significantly above thatexpected due to its location on a colluvium wedge at the baseof the volcanic rock Port Hills. Figure 12F also illustrates thehigh-frequency ground motion on bedrock at Lyttelton Port862 Seismological Research Letters Volume 82, Number 6 November/December 2011