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Images for Edge; more images...

Images, UC QuakeStudies

A photograph of the location of the Green Room garden on Colombo Street. White picket fences have been placed around the edges of the site and a platform has been partially constructed in the back-right corner. Wire fences have been placed around the entire section as a cordon.Crack'd for Christchurch comments, "The Green Room was built by Jonathan Hall and planted by Gina Payne."

Images, UC QuakeStudies

An aerial photograph of the Christchurch central city. The photograph has been captioned by BeckerFraserPhotos, "High Street runs across this photograph in the top third from the old Majestic Theatre at the intersection of Manchester and Lichfield Streets to the intersection of Madras and St Asaph Street which is just beyond the edge of the photo".

Images, UC QuakeStudies

A photograph depicting two 'All Righties' and a tree on the edge of Avondale Park. Posters promoting the AWA Trails and the 'Five Ways to Wellbeing' have been attached to the tree. The photograph was taken on the inaugural walk for the Chisnallwood Trail as part of the AWA Trails launch at Chisnallwood Intermediate. All Right? posted the photograph on their Facebook page on 2 September 2015 at 3:56pm.

Images, UC QuakeStudies

A photograph of the location of the Green Room garden on Colombo Street. White picket fences have been placed around the edges of the site and a platform has been constructed in the back-right corner. Two garden plots have been sectioned off using bricks to the right and front of the site. The front plot has been planted with shrubs and grass. A path leading between the gardens up to the platform has been filled with gravel. Wire fences have been placed around the entire section as a cordon.Crack'd for Christchurch comments, "The Green Room was built by Jonathan Hall and planted by Gina Payne."

Research papers, University of Canterbury Library

Damage distribution maps from strong earthquakes and recorded data from field experiments have repeatedly shown that the ground surface topography and subsurface stratigraphy play a decisive role in shaping the ground motion characteristics at a site. Published theoretical studies qualitatively agree with observations from past seismic events and experiments; quantitatively, however, they systematically underestimate the absolute level of topographic amplification up to an order of magnitude or more in some cases. We have hypothesized in previous work that this discrepancy stems from idealizations of the geometry, material properties, and incident motion characteristics that most theoretical studies make. In this study, we perform numerical simulations of seismic wave propagation in heterogeneous media with arbitrary ground surface geometry, and compare results with high quality field recordings from a site with strong surface topography. Our goal is to explore whether high-fidelity simulations and realistic numerical models can – contrary to theoretical models – capture quantitatively the frequency and amplitude characteristics of topographic effects. For validation, we use field data from a linear array of nine portable seismometers that we deployed on Mount Pleasant and Heathcote Valley, Christchurch, New Zealand, and we compute empirical standard spectral ratios (SSR) and single-station horizontal-to-vertical spectral ratios (HVSR). The instruments recorded ambient vibrations and remote earthquakes for a period of two months (March-April 2017). We next perform two-dimensional wave propagation simulations using the explicit finite difference code FLAC. We construct our numerical model using a high-resolution (8m) Digital Elevation Map (DEM) available for the site, an estimated subsurface stratigraphy consistent with the geomorphology of the site, and soil properties estimated from in-situ and non-destructive tests. We subject the model to in-plane and out-of-plane incident motions that span a broadband frequency range (0.1-20Hz). Numerical and empirical spectral ratios from our blind prediction are found in very good quantitative agreement for stations on the slope of Mount Pleasant and on the surface of Heathcote Valley, across a wide range of frequencies that reveal the role of topography, soil amplification and basin edge focusing on the distribution of ground surface motion.