Following the 2010/2011 Canterbury, New Zealand earthquakes, a detailed door-to-door survey was conducted in the Christchurch region to establish the earthquake performance of lightweight timber-framed residential dwellings with a masonry veneer external cladding system. The post-earthquake survey involved documenting the condition of dwellings in areas that had experienced different levels of earthquake shaking, allowing comparison between the performance of different veneer systems and different shaking intensities. In total, just fewer than 1,100 residential dwellings were inspected throughout the wider Christchurch area. The survey included parameters such as level of veneer damage, type of veneer damage, observed crack widths, and level of repair required. It is concluded that based on observed earthquake performance at the shaking intensities matching or exceeding ultimate limit state loading, the post-1996 veneer fixing details performed satisfactorily and continued use of the detail is recommended without further modification. AM - Accepted Manuscript
In this paper we apply Full waveform tomography (FWT) based on the Adjoint-Wavefield (AW) method to iteratively invert a 3-D geophysical velocity model for the Canterbury region (Lee, 2017) from a simple initial model. The seismic wavefields was generated using numerical solution of the 3-D elastodynamic/ visco- elastodynamic equations (EMOD3D was adopted (Graves, 1996)), and through the AW method, gradients of model parameters (compression and shear wave velocity) were computed by implementing the cross-adjoint of forward and backward wavefields. The reversed-in-time displacement residual was utilized as the adjoint source. For inversion, we also account for the near source/ station effects, gradient precondition, smoothening (Gaussian filter in spatial domain) and optimal step length. Simulation-to-observation misfit measurements based on 191 sources at 78 seismic stations in the Canterbury region (Figure 1) were used into our inversion. The inversion process includes multiple frequency bands, starting from 0-0.05Hz, and advancing to higher frequency bands (0-0.1Hz and 0-0.2Hz). Each frequency band was used for up to 10 iterations or no optimal step length found. After 3 FWT inversion runs, the simulated seismograms computed using our final model show a good matching with the observed seismograms at frequencies from 0 - 0.2 Hz and the normalized least-squared misfit error has been significantly reduced. Over all, the synthetic study of FWT shows a good application to improve the crustal velocity models from the existed geological models and the seismic data of the different earthquake events happened in the Canterbury region.
