Damage ratios for plant, equipment and stock in the 1987 Edgecumbe, New Zealand earthquake
This paper describes an analysis of damage costs to commercial and industrial equipment (plant) and stock in the Mw=6.6 Edgecumbe, New Zealand, earthquake of 2 March 1987. The damage costs were converted to damage ratios by dividing by the value of the relevant property parcel. The mean value and statistical distribution of damage ratios were found for various classes of equipment and stock in the MM7 and MM9 intensity Zones. The lognormal distribution generally fitted the data well.
Equipment and stock are much more variable in nature than modern buildings, and in large part are not designed for earthquakes. In this study they were analysed in subsets formed by classification according to Use (i.e. shops, offices, halls, residential or industrial) and Vulnerability (i.e. Robust, Medium or Fragile). These classifications provided useful insights into variations in the damage ratio. The overall mean damage ratio, Drm for stock was considerably higher than for equipment, even though Drm for Fragile equipment was higher than Drm for Fragile stock. This occurred because the proportion of stock that was Fragile was much larger than the corresponding proportion of equipment. The proportional difference in damage levels between Fragile and Robust property was greater at intensity MM7 than at MM9. This is consistent with the definitions of the Modified Mercalli scale. A comparison of the damage to equipment and buildings showed that, at MM9, the mean and distribution of damage ratios for Medium vulnerability equipment are similar to those for the associated single storey, post-code (1935+) commercial and industrial buildings.
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Copyright (c) 1995 D. J. Dowrick, D. A. Rhoades
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