The aim of this poster is to examine the seismic response of two structural systems when subjected to observed and simulated ground motions (GMs) for the 22 February 2011 (22Feb2011) Christchurch earthquake (Razafindrakoto et al. (2018)) via an automated workflow. The layout and technical details of the automated workflow are described at Motha et. al. (2019).
This study provides an initial examination of source parameter uncertainty in a New Zealand ground motion simulation model, by simulating multiple event realisations with perturbed source parameters. Small magnitude events in Canterbury have been selected for this study due to the small number of source input parameters, the wealth of recorded data, and the lack of appreciable off-fault non-linear effects. Which provides greater opportunity to identify systematic source, path and site effects, required to robustly investigate the causes of uncertainty.
A team of earthquake geologists, seismologists and engineering seismologists from GNS Science, NIWA, University of Canterbury, and Victoria University of Wellington have collectively produced an update of the 2002 national probabilistic seismic hazard (PSH) model for New Zealand. The new model incorporates over 200 new onshore and offshore fault sources, and utilises newly developed New Zealand-based scaling relationships and methods for the parameterisation of the fault and subduction interface sources. The background seismicity model has also been updated to include new seismicity data, a new seismicity regionalisation, and improved methodology for calculation of the seismicity parameters. Background seismicity models allow for the occurrence of earthquakes away from the known fault sources, and are typically modelled as a grid of earthquake sources with rate parameters assigned from the historical seismicity catalogue. The Greendale Fault, which ruptured during the M7.1, 4 September 2010 Darfield earthquake, was unknown prior to the earthquake. However, the earthquake was to some extent accounted for in the PSH model. The maximum magnitude assumed in the background seismicity model for the area of the earthquake is 7.2 (larger than the Darfield event), but the location and geometry of the fault are not represented. Deaggregations of the PSH model for Christchurch at return periods of 500 years and above show that M7-7.5 fault and background source-derived earthquakes at distances less than 40 km are important contributors to the hazard. Therefore, earthquakes similar to the Darfield event feature prominently in the PSH model, even though the Greendale Fault was not an explicit model input.
On 4 September 2010, a magnitude Mw 7.1 earthquake struck the Canterbury region on the South Island of New Zealand. The epicentre of the earthquake was located in the Darfield area about 40 km west of the city of Christchurch. Extensive damage occurred to unreinforced masonry buildings throughout the region during the mainshock and subsequent large aftershocks. Particularly extensive damage was inflicted to lifelines and residential houses due to widespread liquefaction and lateral spreading in areas close to major streams, rivers and wetlands throughout Christchurch and Kaiapoi. Despite the severe damage to infrastructure and residential houses, fortunately, no deaths occurred and only two injuries were reported in this earthquake. From an engineering viewpoint, one may argue that the most significant aspects of the 2010 Darfield Earthquake were geotechnical in nature, with liquefaction and lateral spreading being the principal culprits for the inflicted damage. Following the earthquake, a geotechnical reconnaissance was conducted over a period of six days (10–15 September 2010) by a team of geotechnical/earthquake engineers and geologists from New Zealand and USA (GEER team: Geo-engineering Extreme Event Reconnaissance). JGS (Japanese Geotechnical Society) members from Japan also participated in the reconnaissance team from 13 to 15 September 2010. The NZ, GEER and JGS members worked as one team and shared resources, information and logistics in order to conduct thorough and most efficient reconnaissance covering a large area over a very limited time period. This report summarises the key evidence and findings from the reconnaissance.
John Townend is an Associate Professor at the School of Geography, Environment and Earth Sciences.
A large crack in the ground at Sullivan Park in Avonside which has resulted from the 4 September 2010 earthquake. Remnants of liquefaction silt can be seen around the edges of the crack.
Photograph captioned by BeckerFraserPhotos, "Avonside Drive footpath".
A photograph of a damaged bridge. The photograph is captioned by BeckerFraserPhotos, "Askeaton Drive, Kaiapoi".
A large crack in the ground at Sullivan Park in Avonside which has resulted from the 4 September 2010 earthquake. Remnants of liquefaction silt can be seen around the edges of the crack.
Photograph captioned by BeckerFraserPhotos, "Dyers Road under reconstruction, adding about 30 cm to its elevation".
A damaged brick house on Avonside Drive.
A substantial crack in the lawn of a house on Avonside Drive.
The north end of the bridge on Gayhurst Road. During the earthquake, the bridge was forced about 15 centimetres towards the river, the land falling away under the road. Fencing has been placed around the footpath, and the road filled and resealed so that it can still be used by traffic.
Cracking along the pavement at Halswell Primary School. The ground has risen and fallen in places leaving an uneven surface where the children usually play.
This study investigates the uncertainty of simulated earthquake ground motions for smallmagnitude events (Mw 3.5 – 5) in Canterbury, New Zealand. 148 events were simulated with specified uncertainties in: event magnitude, hypocentre location, focal mechanism, high frequency rupture velocity, Brune stress parameter, the site 30-m time-averaged shear wave velocity (Vs30), anelastic attenuation (Q) and high frequency path duration. In order to capture these uncertainties, 25 realisations for each event were generated using the Graves and Pitarka (2015) hybrid broadband simulation approach. Monte-Carlo realisations were drawn from distributions for each uncertainty, to generate a suite of simulation realisations for each event and site. The fit of the multiple simulation realisations to observations were assessed using linear mixed effects regression to generate the systematic source, path and site effects components across all ground motion intensity measure residuals. Findings show that additional uncertainties are required in each of the three source, path, and site components, however the level of output uncertainty is promising considering the input uncertainties included.
Shows a hand lifting a house up from the ground, as the earth shakes and rumbles around it. A voice in the earth says, 'I'm still here'. Refers to ongoing earthquakes and aftershocks following the devastating 2010 and 2011 earthquakes in Canterbury. Quantity: 1 digital cartoon(s).
Photograph captioned by Fairfax, "Nick Wright (9) explores a huge crack in the earth in Charles Street, Kaiapoi".
Photograph captioned by Fairfax, " Nick Wright (9) explores a huge crack in the earth in Charles Street, Kaiapoi".
John Townend is an Associate Professor at the School of Geography, Environment and Earth Sciences at Victoria University Wellington.
John Townend is an Associate Professor at the School of Geography, Environment and Earth Sciences at Victoria University Wellington.
Damage to a house in Redcliffs, which has lost its cladding. The earth bank below the house has collapsed.
A broken footpath in Kaiapoi where the earth has slumped under the concrete during the September 4th earthquake.
Photograph captioned by BeckerFraserPhotos, "Avonside Drive".
Cracks along the driveway and lawn of a property on Avonside Drive.
Cracks along the road in Avonside Drive. The riverbank has slumped towards the river, separating the land from the road and creating these cracks. Road cones warn drivers of the uneven surface. In the distance, a pile of liquefaction can be seen in front of a house.
A large crack running through the driveway and lawn of a property on Avonside Drive.
The driveway of a house on Avonside Drive. One of the concrete slabs has lifted and the owner has tried to fill the gap with blocks of wood. Unfortunately, these have come loose and are sticking out of the hole.
Photograph captioned by BeckerFraserPhotos, "Cracks in the footpath outside 308 Avonside Drive".
In the aftermath of the 2010-2011 Canterbury Earthquake Sequence (CES), the location of Christchurch-City on the coast of the Canterbury Region (New Zealand) has proven crucial in determining the types of- and chains of hazards that impact the city. Very rapidly, the land subsidence of up to 1 m (vertical), and the modifications of city’s waterways – bank sliding, longitudinal profile change, sedimentation and erosion, engineered stop-banks… - turned rainfall and high-tides into unprecedented floods, which spread across the eastern side of the city. Within this context, this contribution presents two modeling results of potential floods: (1) results of flood models and (2) the effects of further subsidence-linked flooding – indeed if another similar earthquake was to strike the city, what could be the scenarios of further subsidence and then flooding. The present research uses the pre- and post-CES LiDAR datasets, which have been used as the boundary layer for the modeling. On top of simple bathtub model of inundation, the river flood model was conducted using the 2-D hydrodynamic code NAYS-2D developed at the University of Hokkaido (Japan), using a depth-averaged resolution of the hydrodynamic equations. The results have shown that the area the most at risk of flooding are the recent Holocene sedimentary deposits, and especially the swamplands near the sea and in the proximity of waterways. As the CES drove horizontal and vertical displacement of the land-surface, the surface hydrology of the city has been deeply modified, increasing flood risks. However, it seems that scientists and managers haven’t fully learned from the CES, and no research has been looking at the potential future subsidence in further worsening subsidence-related floods. Consequently, the term “coastal quake”, coined by D. Hart is highly topical, and most especially because most of our modern cities and mega-cities are built on estuarine Holocene sediments.
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