Photograph by Jocelyn Kinghorn 191
Images, UC QuakeStudies
Build up of liquefaction that has seeped from the ground onto the road and footpath.
Build up of liquefaction that has seeped from the ground onto the road and footpath.
A 'sand volcano' of liquefaction silt in Bexley. The photographer comments, "Liquefaction is just a mixture of sand and water squeezed up from the ground, but with a little imagination it has a beauty in its untouched state".
A motion-blurred photograph of houses, with the Port Hills in the background. The photographer comments, "This I hope gives you a feel of what it feels like in an earthquake. When you spend your whole life thinking that you and your home are built on solid ground, it can be quite a shock when you find it is not. You can feel the house shaking like a dog with a toy, rising up violently underneath you or the most gentle form which is when the ground moves gently like a wave moving under a rowing boat. It is not just the movement, you often get a rumbling sound which can precede a violent shake or can result in no movement at all. This means that some vehicles can sound like the rumbling initially and in the early days would get your heart racing. Another form of stress is when big excavators as heavy as a tank move as you can feel the ground shake from streets away, but you do not always hear the engine. For most of us the problem when the shaking starts, is wondering if this is the start of an extremely violent earthquake or will it peter out".
The previously unknown Greendale Fault ruptured to the ground surface, causing up to 5 metres horizontal and 1 metre vertical permanent offset of the ground, during the September 2010 Darfield (Canterbury) earthquake. Environment Canterbury commissioned GNS Science, with help from the University of Canterbury, to define a fault avoidance zone and to estimate the fault recurrence interval. There is little evidence for past movement on the fault in the past 16,000 years. However, because of the uncertainties involved, a conservative approach was taken and the fault has been categorised as a Recurrence Interval Class IV fault (a recurrence interval of between 5,000 and 10,000 years). A PhD study by a University of Canterbury student will work towards refining the Recurrence Interval Class over the next three years. Taking a risk-based approach, the Ministry for the Environment Active Fault Guidelines recommend that normal residential development be allowed within the fault avoidance zone for faults of this Recurrence Interval Class, but recommends restrictions for larger community buildings or facilities with post-disaster functions. The report is assisting Selwyn District Council in granting consents for rebuilding houses on or near the Greendale Fault that were damaged by permanent distortion of the ground due to the fault rupture in the September 2010 earthquake. The report provides specific recommendations for building on or close to the Greendale Fault, which are being implemented by Selwyn District Council. See Object Overview for background and usage information.
Two images of a house, taken before and after the earthquakes. In the after photograph the chimneys are gone, a column supporting the car port has partly collapsed, windows are broken, and the previously neat lawn and driveway are overgrown. The photographer comments, "This was a house that I was selling up to the September 2010 earthquake in Christchurch. It was on Avonside Drive, which was an area that has been badly hit in every earthquake that has hit the area. In the September quake parts of the house moved in different directions and one of the upstairs doors had to be smashed open to release one of the sons from his bedroom. This occurred in the dark with numerous aftershocks shaking the house. Liquefaction poured up through the floor and flowed down the drive. Everyone got out OK, but soon after the house was red stickered meaning it was dangerous to enter. The house was looted many times even though there was constant police patrols. When the most violent earthquake occurred on 22 February 2012 both the tall heavy chimneys came crashing through into the living areas. Subsequent earthquakes and aftershocks have caused one of the brick fence pillars to fall and the front garage pillar to break up and twist. The family's troubles did not end there. They moved into the home of one of their parents and this mansion of a home was so badly affected by the February earthquake that no one could enter to collect any of their or their parents' belongings. They now own a new home, which they are fond of except when the ground shakes yet again. There has been to date 10,712 earthquakes and aftershocks since 4 September 2010".
Extended Direct Analysis (EDA), developed at the University of Canterbury, is an advance on the AISC Direct Analysis method for the analysis of frames subjected to static forces. EDA provides a faster, simple and more rational way to properly consider the second-order effects, initial residual stresses (IRS) and the initial imperfections or steel structures under one directional loading than conventional analysis methods. This research applied the EDA method to quantify the effect of member overstrength on frame behaviour for a single storey frame. Also, the effects of IRS, which were included in the EDA static analysis, but which are not considered explicitly in non-linear seismic analysis, were evaluated in two ways. Firstly, they were considered for simple structures subject to increasing cyclic displacement in different directions. Secondly, incremental dynamic analysis with realistic ground motion was used to quantify the likely effect of IRS in earthquakes. It was found that, contrary to traditional wisdom and practice, greater member strengths can result in lower frame strengths for frames under monotonic lateral loading. The structural lateral capacity of the overstrength case was reduced by 6% compared to the case using the dependable member strengths. Also, it resulted significantly different in member demands. Therefore, it is recommended that when either plastic analysis or EDA is used, that both upper and lower bounds on the likely member strength should be considered to determine the total frame strength and the member demands. Results of push-pull analysis under displacement control showed that for IRS ratio, gamma < 0.5 and axial compressive force ratio, N*/Ns, up to 0.5, IRS did affect the structural behaviour in the first half cycle. However, the behavior in the later cycles was not significantly affected. It also showed that the effect of initial residual stresses in the frame was less significant than for the column alone when the column was subjected to similar axial compressive force. The incremental dynamic analysis results from both cantilever column and the three-storey steel frame showed that by increasing gamma = 0 to 0.5, the effect of IRS on seismic responses, based on the 50% confidence level, was less than 3% for N*/Ns, up to 0.5.
Questions to Ministers 1. Hon PHIL GOFF to the Prime Minister: In stating that "this Government introduced a balanced package of tax cuts" was he saying that his tax changes and the tax system are fair to all New Zealanders? 2. LOUISE UPSTON to the Minister of Finance: What will be the main objectives of Budget 2011 tomorrow? 3. Hon ANNETTE KING to the Prime Minister: When he said "in most cases the tax switch more than compensated people for the increase in GST", in which cases hadn't people been fully compensated? 4. JOHN BOSCAWEN to the Prime Minister: Does he stand by the statement he made in his post-Cabinet press conference on Monday that "Everyone needs to understand that what Don Brash is talking about is hardcore"; if so why? 5. Hon DAVID CUNLIFFE to the Minister of Finance: What is the total impact on the operating balance, over the forecast period, of the fiscal impact of the tax changes in Budget 2010 according to page 70 of the 2010 Budget and Economic Fiscal Update, and how does he reconcile that with the Prime Minister's statement in the House yesterday that "National's tax plan 2010…was fiscally neutral"? 6. ALLAN PEACHEY to the Minister of Corrections: What reports has she received about the first year of container units being used in New Zealand prisons? 7. RAHUI KATENE to the Minister for Communications and Information Technology: What was the motivation behind the decision to remove regulatory forbearance from the Telecommunications (TSO, Broadband, and Other Matters) Amendment Bill? 8. JACINDA ARDERN to the Minister for Canterbury Earthquake Recovery: Does he stand by the Prime Minister's statement in relation to Christchurch that "it looks like the residential rebuild alone will require up to 12,500 full-time workers", if not, how many full-time workers does he believe will now be needed? 9. Hon TAU HENARE to the Minister for Social Development and Employment: What recent announcements has she made to support community social services? 10. CLARE CURRAN to the Minister for Communications and Information Technology: What is the best estimate of the additional cost to the Crown of the change he announced to the ultrafast broadband network this morning? 11. TIM MACINDOE to the Minister of Housing: What recent announcements has he made regarding the Government's Housing Innovation Fund? 12. GARETH HUGHES to the Acting Minister of Energy and Resources: What is her response to the statement of leading scientist and NASA director Dr James Hansen, currently touring New Zealand, that "coal is the single greatest threat to civilisation and all life on our planet" and we should leave it in the ground?