2013 – Development of design ground motions for the Tekapo Canal Project

Paul Somerville

Earthquake ground motions were developed for the Tekapo Canal Remediation Project, including both Canal and Bridge sites. This work involved the specifications of the parameters of active faults and seismic source zones, the development of an aftershock sequence, and the review and selection of suitable ground motion prediction equations. The seismic hazard at the project sites is dominated by earthquakes occurring on the Irishman Creek fault. The characteristics of an inferred active (unnamed) fault shown crossing the Tekapo Canal near Forks Stream and the hazard it poses to the canal were also assessed, and it was concluded that there was no need to further investigate it as part of the canal upgrade project. A probabilistic seismic hazard analysis was used to develop response spectra for mainshock events for the various return periods relevant to components of the canal system having different PIC categories. A deterministic seismic hazard analysis methodology was used to estimate the aftershock spectra. Depending on the PIC category, time histories were developed to represent the response spectrum for both mainshock and aftershock events at some canal sites.