This report describes the observations and assessments of the team members on the effects of the earthquake on the ground, buildings and other structures, lifelines and the local community. Comment is made on the response to the earthquake and lessons are drawn for the New Zealand situation.

The assumptions and methods of analysis used to define the flexural strength and the available limit curvature of reinforced concrete columns sections are discussed. The results of cyclic moment-curvature analyses of a large range of reinforced concrete column sections, using cyclic stress-strain relationships for the steel and for the concrete, are outlined and the important variables and their influence on the available strength and curvature ductility are identified. Examples of design charts derived from these analytical results are discussed and a flow chart outlining the whole seismic resistance design procedure for bridge piers is introduced. The quantity of confining steel determined using the design charts is compared with the corresponding quantity required by the current New Zealand concrete design code equations. Finally a possible future development is discussed that would lead to an improvement of the code design method used to provide sufficient ductility in the plastic hinges of reinforced concrete columns.

On 22 February 2011 the Mw6.2 Christchurch earthquake occurred with an epicentre less than 10 km from the Christchurch Central Business District (CBD) on an unknown buried fault at the edge of the city. The majority of damage was a result of lateral spreading along the Avon and Heathcote Rivers, with few bridges damaged due to ground shaking only. The most significant damage was to bridges along the Avon River, coinciding with the areas of the most severe liquefaction, with less severe liquefaction damage developing along the Heathcote River. Most affected were bridge approaches, abutments and piers, with a range of damage levels identified across the bridge stock. In the days following the earthquake, teams from various organizations performed inspections on over 800 bridges throughout the affected Canterbury region. This paper details the preliminary findings based on visual inspections and some preliminary analyses of highway and road bridges. The paper comprises information supplied by consulting engineering firms which were also directly involved in the inspections soon after the earthquake.

Seismic isolation of structures has been applied in New Zealand since 1973. To date approximately 45 bridges, 3 large buildings and a few other structures have been protected with this technique. These include 40 bridges and 2 buildings designed by Works and Development Services Corporation (NZ) Ltd (WORKS). Numerous energy dissipating devices have been developed and tested by New Zealand researchers. Six of these designs have proved to be convenient and economical and have been incorporated in the seismic isolation systems of the structures built. Development work on seismic isolation devices is continuing in New Zealand and contact with specialists from other countries - in particular from Japan and the United States of America - is being maintained. Seismic isolation has been found to be a cost effective means of mitigating earthquake effects, particularly if the long term benefits of reduced seismic damage and disruption are taken into consideration.

The earthquake which shook Gisbome at 21.46h on 10 August 1993 was reportedly alarming to local residents and was felt widely across the North Island. The event is described separately in more detail in this Bulletin. Briefly, the earthquake has been preliminarily assigned a magnitude of ML 6.4 with a focal depth of 70 km. The epicentre was located 20 to 25 km north of Gisbome. Reports from the area were of only light building damage, and of bridging generally experiencing few problems, except that single lane traffic operations were necessary on two state highway bridges for a period after the event.