Vulnerability and seismic risk assessment of buildings following the 1989 Newcastle, Australia earthquake

Abstract

Ten days after the Newcastle, Australia earthquake of 28 December, 1989, the UK-based Earthquake Engineering Field Investigation Team (EEFIT) mounted a five day mission to the affected area. This paper presents the findings of the EEFIT investigation and subsequent follow up studies in relation to the extent of building damage and its distribution within the City of Newcastle and the surrounding urban area. Results are based on both detailed street surveys and general damage surveys, the former carried out in two areas, namely the heavily damaged suburban district of Hamilton (3km west of the city centre) and the Newcastle central business district. The findings of these surveys have provided valuable information on the vulnerability of building stock of types common to other parts of Australia, the UK and elsewhere, and hence form an important database for the accurate assessment of seismic risk to buildings in regions of low seismicity. This information will assist the development of realistic, economical seismic code provisions for building design and construction in low-risk areas. An important feature arising from the surveys and subsequent analytical studies of site response in the heavily damaged districts within the Hunter River alluvial basin is that, contrary to reports published by the Institution of Engineers, Australia amongst others, the areas of deep alluvial soil and fill do not correlate strongly with the more heavily damaged districts determined from post-earthquake assessments. Hence, suggestions that this form of site soil amplification effect played a major part in the distribution and extent of heavy damage in this earthquake are somewhat misleading for the future development of planning and design regulations. Furthermore, the results of site response analyses show that it is more likely to be the shallower soils near the border of the alluvial basin which tend to amplify bedrock ground motions generated by this type of earthquake.