9.b Canterbury Earthquakes
Survey of Damage Extent and Severity of Christchurch Earthquakes for Regional Risk Assessment
T. Lai, A. Nasseri & F. Turner
After the two recent earthquakes in Christchurch (September 2010 and February 2011) a team of researchers organized by the Earthquake Engineering Research Institute (EERI) was dispatched to the area to conduct a damage survey. The survey addressed a variety of interests including structural and geotechnical engineering, emergency management, disaster recovery and socio-economic impacts. The authors focused on identifying the spread and severity of damage by sampling areas in order to capture the overall performance of buildings and to estimate economic and insured losses.
Several locations close to seismic recording stations were visited and information about building attributes and the state of structural and non-structural damage for about 200 buildings, mostly typical non-engineered dwellings and a few engineered structures, were collected. This paper presents some statistics of the observed damage for typical residential dwellings around Christchurch. Results from this study suggest a low level of shaking-induced damage for wood structures during these earthquakes.
Performance of house lining and cladding systems in the 22 February Lyttleton earthquake
G.C. Thomas & R.H. Shelton
The February 22nd earthquake resulted in much damage to houses from lateral spreading and liquefaction, but with the epicentre close to the hill suburbs and Lyttelton substantial shaking damage to houses occurred. Shaking damage in flatter areas was generally less due to the distance from the epicentre. Also, the slab on ground and low piled foundations with concrete walls on the flat in Christchurch provided a behavioural advantage. Although the intensity of the shaking was similar to what might be expected from a larger earthquake on a fault such as the Wellington fault the duration was short. Despite the short duration of shaking some houses moved on foundations and damage to foundation walls occurred. Poor construction was observed to result in increased levels of damage. At least some damage to brick claddings was very common, but mostly limited to cracking with little damage to flexible claddings such as weatherboard. Newer brick veneer appeared to perform better. Most damage to linings was at sheet joints in gypsum plasterboard, and cracks from opening corners with diagonal cracking more common in lathe and plaster and fibrous plaster linings. The paper will describe the behaviour of houses affected by shaking rather than liquefaction.
Christchurch City lifelines - performance of concrete potable water reservoirs in the February 2011 Christchurch Earthquake and summary findings
N. Charman & I. Billings
The magnitude Mw 6.2-6.3 earthquake that occurred in Christchurch on 22 February 2011 resulted in widespread damage to buildings and infrastructure.
Christchurch City's concrete reservoirs in the Port Hills and Cashmere Hills are located near the epicentre of the February earthquake and suffered damage of varying extent from nil through to major. Of 43 reservoirs, two were declared inoperable (including Christchurch's largest), three barely operable and requiring major repair works and a further fifteen reservoirs requiring lesser repair. The city lost 40% of its potable water storage as a result.
The Port Hills and Cashmere Hills concrete reservoirs are of varying vintage, construction type and storage capacity. These reservoirs form a useful database for assessment of performance in the February 2011 Christchurch Earthquake and also against current design standards.
Damaged roof-to-wall connections were observed in many reservoirs with damage to other elements such as walls, internal columns, base-slabs and wall-to-base connections observed in fewer reservoirs. Detailed seismic assessments, on eight of the reservoirs, are commonly identifying vulnerabilities with roof-to-wall and wall-to-base/foundation connections and therefore indicating reasonable correlation with the damage observed. Significant geotechnical issues were also observed at three of the reservoir sites.
A summary of damage observed and the performance of critical structural connections / details are presented in this paper along with reinstatement progress and key lessons learned. Key findings are that robustness in roof-to-wall and wall-to-base connections, the avoidance of joints in floor slabs and a suitable wall thickness provide increased reliability.
“Recovery of Lifelines” following the 22nd February 2011 Christchurch Earthquake: successes and issues
Sonia Giovinazzi & Thomas M. Wilson
The devastating magnitude M6.3 earthquake, that struck the city of Christchurch at 12:51pm on Tuesday 22 February 2011, caused widespread damage to the lifeline systems. Following the event, the Natural Hazard Research Platform (NHRP) of New Zealand funded a short-term project “Recovery of Lifelines” aiming to: 1) coordinate the provision of information to meet lifeline short-term needs; and to 2) facilitate the accessibility to lifelines of best practice engineering details, along with hazards and vulnerability information already available from the local and international scientific community. This paper aims to briefly summarise the management of the recovery process for the most affected lifelines systems, including the electric system, the road, gas, and the water and wastewater networks. Further than this, the paper intends to discuss successes and issues encountered by the “Recovery of Lifelines” NHRP project in supporting lifelines utilities.
The Impact of the 22nd February 2011 Earthquake on Christchurch Hospital
J.K. McIntosh, C. Jacques, J. Mitrani-Reiser, T.D. Kirsch, S. Giovinazzi & T.M. Wilson
The 22nd February 2011, Mw 6.3 Christchurch earthquake in New Zealand caused major damage to critical infrastructure, including the healthcare system. The Natural Hazard Platform of NZ funded a short-term project called 'Hospital Functions and Services' to support the Canterbury District Health Board's (CDHB) efforts in capturing standardized data that describe the effects of the earthquake on the Canterbury region's main hospital system. The project utilised a survey tool originally developed by researchers at Johns Hopkins University (JHU) to assess the loss of function of hospitals in the Maule and Bio-Bio regions following the 27th February 2010, Mw 8.8 Maule earthquake in Chile. This paper describes the application of the JHU tool for surveying the impact of Christchurch earthquake on the CDHB Hospital System, including the system's residual capacity to deliver emergency response and health care. A short summary of the impact of the Christchurch earthquake on other CDHB public and private hospitals is also provided. This study demonstrates that, as was observed in other earthquakes around the world, the effects of damage to non-structural building components, equipment, utility lifelines, and transportation were far more disruptive than the minor structural damage observed in buildings (FEMA 2007). Earthquake related complications with re-supply and other organizational aspects also impacted the emergency response and the healthcare facilities' residual capacity to deliver services in the short and long terms.
Christchurch Cathedral of the Blessed Sacrament: Lessons learnt on the Stabilisation of a Significant Heritage Building
J. Lester, A.G. Brown & J.M. Ingham
ABSTRACT: The Catholic Cathedral of the Blessed Sacrament is a category 1 listed heritage building constructed largely of unreinforced stone masonry, and was significantly damaged in the recent Canterbury earthquakes. The building experienced ground shaking in excess of its capacity leading to block failures and partial collapse of parts of the building, which left the building standing but still posing a significant hazard. In this paper we discuss the approach to securing the building, and the interaction of the structural, heritage and safety demands involved in a dynamic seismic risk environment. We briefly cover the types of failures observed and the behaviour of the structure, and investigate the performance of both strengthened and un-strengthened parts of the building. Seismic strengthening options are investigated at a conceptual level. We draw conclusions as to how the building performed in the earthquakes, comment on the effectiveness of the strengthening and securing work and discuss the potential seismic strengthening methods.