Assessment of Seismic Ground Response Analysis Model Uncertainty at Christchurch Cathedral College, Christchurch Central Business District, New Zealand-Video

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Video Summary

The presentation describes seismic ground-response analysis for Kotui, Christchurch’s planned multi-use arena. The team developed site-specific probabilistic seismic hazard and amplification models, using recorded motions from the 2010 Darfield and 2011 Christchurch earthquakes at a nearby station to evaluate uncertainty in 1D ground-response analyses.<br /><br />Using local CPT and shear-wave-velocity data, the presenter tested four ground profiles, focusing on a soft silty layer at roughly 20–25 metres depth. Profiles that used the measured low velocity for this layer substantially under-predicted observed short- and moderate-period motions. Increasing its modeled velocity improved the match. The presenter attributed this to the layer’s variable thickness and properties across the area: a 1D profile may not capture three-dimensional pathways through stiffer ground.<br /><br />Residuals from the analyses were combined to represent additional uncertainty in the amplification factors, adding approximately 0.3. The work highlights the value of earthquake recordings and shared geotechnical databases in refining site-specific models.

Keywords

seismic ground-response analysis

Christchurch arena

site-specific seismic hazard

1D ground-response models

shear-wave velocity

ground amplification uncertainty