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1. Background and Objectives This poster presents results from ground motion simulations of small-to-moderate magnitude (3.5≤Mw≤5.0) earthquake events in the Canterbury, New Zealand region using the Graves and Pitarka (2010,2015) methodology. Subsequent investigation of systematic ground motion effects highlights the prediction bias in the simulations which are also benchmarked against empirical ground motion models (e.g. Bradley (2013)). In this study, 144 earthquake ruptures, modelled as point sources, are considered with 1924 quality-assured ground motions recorded across 45 strong motion stations throughout the Canterbury region, as shown in Figure 1. The majority of sources are Mw≥4.0 and have centroid depth (CD) 10km or shallower. Earthquake source descriptions were obtained from the GeoNet New Zealand earthquake catalogue. The ground motion simulations were performed within a computational domain of 140km x 120km x 46km with a finite difference grid spacing of 0.1km. The low-frequency (LF) simulations utilize the 3D Canterbury Velocity Model while the high-frequency (HF) simulations utilize a generic regional 1D velocity model. In the LF simulations, a minimum shear wave velocity of 500m/s is enforced, yielding a maximum frequency of 1.0Hz.
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These were scattered across the park.
Robbie watches a sand volcano smother his driveway.
A photograph of the earthquake damage to the Canterbury Television Building on Gloucester Street. There are large cracks in the columns of the building and many of the windows are broken.
This has made a huge mess for the residents to clean up. I heard on the news that homes have been damaged by subsidence in areas of earthquake-caused liquefaction like this.
Lots of people were out and about in the streets checking on everyone after the earthquake. When it was clear that everyone was OK, the sand volcanos became the feature of interest.
Well-validated liquefaction constitutive models are increasingly important as non-linear time history analyses become relatively more common in industry for key projects. Previous validation efforts of PM4Sand, a plasticity model specifically for liquefaction, have generally focused on centrifuge tests; however, pore pressure transducers installed at several free-field sites during the Canterbury Earthquake Sequence (CES) in Christchurch, New Zealand provide a relatively unique dataset to validate against. This study presents effective stress site response analyses performed in the finite difference software FLAC to examine the capability of PM4Sand to capture the generation of excess pore pressures during earthquakes. The characterization of the subsurface is primarily based on extensive cone penetration tests (CPT) carried out in Christchurch. Correlations based on penetration resistances are used to estimate soil parameters, such as relative density and shear wave velocity, which affect liquefaction behaviour. The resulting free-field FLAC model is used to estimate time histories of excess pore pressure, which are compared with records during several earthquakes in the CES to assess the suitability of PM4Sand.
Heathcote Valley school strong motion station (HVSC) consistently recorded ground motions with higher intensities than nearby stations during the 2010-2011 Canterbury earthquakes. For example, as shown in Figure 1, for the 22 February 2011 Christchurch earthquake, peak ground acceleration at HVSC reached 1.4 g (horizontal) and 2 g (vertical), the largest ever recorded in New Zealand. Strong amplification of ground motions is expected at Heathcote Valley due to: 1) the high impedance contrast at the soil-rock interface, and 2) the interference of incident and surface waves within the valley. However, both conventional empirical ground motion prediction equations (GMPE) and the physics-based large scale ground motions simulations (with empirical site response) are ineffective in predicting such amplification due to their respective inherent limitations.
File reference: CCL-2011-11-22-IMG_0784 PODattheShow November2011 From the collection of Christchurch City Libraries.
A photograph of the earthquake damage to the Canterbury Provincial Chambers Buildings on Durham Street. Large sections of the masonry have collapsed, spilling onto the road. Wire fencing has been placed around the building as a cordon. Scaffolding erected up the side of the building after the 4 September 2010 earthquake has collapsed. In the distance, a crane is parked on the street.
Construction materials outside a house on Canterbury Street in Lyttelton. The house is being demolished after the 22 February 2011 earthquake. Wire fencing and road cones cordon off the area, and a bulldozer and a digger are parked on the road.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_012.JPG From the collection of Christchurch City Libraries.
Many buildings with relatively low damage from the 2010-2011 Canterbury were deemed uneconomic to repair and were replaced [1,2]. Factors that affected commercial building owners’ decisions to replace rather than repair, included capital availability, uncertainty with regards to regional recovery, local market conditions and ability to generate cash flow, and repair delays due to limited property access (cordon). This poster provides a framework for modeling decision-making in a case where repair is feasible but replacement might offer greater economic value – a situation not currently modeled in engineering risk analysis.
Sand volcanoes put the silt all over the road.
An usual thing to see coming from the ground in Hoon Hay, Christchurch.
File reference: CCL-2011-11-22-IMG_0783PODattheShow November2011 From the collection of Christchurch City Libraries.
A report created by the University of Canterbury Quake Centre and the University of Auckland, funded by the Building Research Levy. It shows how an innovation process was initiated and managed throughout the rebuilding of the horizontal infrastructure after the Canterbury earthquakes.
A worker in a high visibility vest and a hard hat repairing and strengthening the outside of a building at the University of Canterbury. The photograph has been captioned by BeckerFraserPhotos, "The repair work on the buildings at the University of Canterbury looks similar to the scenes in the CBD".
Container Love: shipping container decorated with knitted and crocheted squares. Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_034.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_013.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_004.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_003.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_010.JPG From the collection of Christchurch City Libraries.
Container Love: shipping container decorated with knitted and crocheted squares. Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_025.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_007.JPG From the collection of Christchurch City Libraries.
Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_005.JPG From the collection of Christchurch City Libraries.