Structural change detection applying long‑term seismic interferometry by deconvolution method to a modern civil engineering structure (New Zealand)

Pulse-wave propagation velocity and resonance frequency measured in civil engineering
structures are both related to structural design. Monitoring their variation following seismic
strong shaking provides information about the immediate building capacity. Joint-interpre-
tation of frequency and velocity variation requires a better understanding of the processes
controlling seismic structural health. In this study, we analysed 8 years of earthquake data
recorded by the vertical array installed in the Te Puni building in Wellington, New Zea-
land, as part of the GeoNet building instrumentation programme. Co-seismic variations
of pulse wave velocity and fundamental frequency are analysed and interpreted through a
Timoshenko beam-like building model. This study shows that even though no structural
damage was visually reported over the considered time of monitoring, co- and post-seismic
variation of both parameters’ values are observed for almost all earthquakes, including a
permanent shift following strong ground shaking. Variations of pulse-wave velocity and
resonance frequency are cross-interpreted in terms of the building model. They reflect a
time variant building response, correlated with the seismic loading. In addition, time delay
of the pulse-wave velocity as a function of the building height provides relevant informa-
tion on the location of the changes and confirms the efficient cross-interpretation of both

methods for seismic Structural Health monitoring.