Earthquakes and Existing Buildings: New Zealand Experience 1968 to 2008

Ever since the Napier earthquake in 1931, New Zealand has taken earthquake engineering seriously. Developments in design standards and seismological knowledge over the years have resulted in a current building stock with a wide variety of expected performance when compared with new building standards. This paper traces the main developments in design since 1935 and the efforts to address deficiencies in older buildings, from the first legislation in 1968, which covered masonry buildings, to the latest experiences with the implementation of the Building Act 2004. The 2004 provisions cover all buildings except small residential building and define the level at which and existing building is regarded as earthquake-prone and thus could be subject to a requirement to "reduce or remove the danger". The Act required each of New Zealand's 73 territorial authorities to develop a policy on earthquake-prone buildings, to consult publicly before adopting it, and to submit it to the Department of Building and Housing. The approach, priorities and details of policies were up to each territorial authority. The paper outlines how New Zealand has sought to reduce earthquake risk in existing buildings over the last 40 years and to deal with the complex mix of technical, social, heritage and economic issues involved. It is hoped that this examination of the New Zealand experience will be instructive to those in other countries seeking to address the risks represented by existing buildings.