| It was noticed that the numbers of victims from natural disasters (earthquakes, floods, hurricanes etc.) as well as losses from disasters have a tendency to a non-linear increase with time. This effect is commonly related to the rate of population growth, to spreading of potentially dangerous technologies and to environment degradation. Thus, the process is assumed to be non-stationary which evidently interferes with the idea of the sustainable development of society. However, the alternative model of this effect can be suggested. We have shown that the non-linear growth of cumulative losses from earthquakes and floods is connected with the ″heavy tail″ in the loss distribution rather than with a change in distribution or occurrence rate of disasters, the latter being of minor importance. This effect occurs in the cases when distribution function F(x) of losses has a ″heavy tail″. In such cases it can be described satisfactorily by the Pareto distribution: F(x)=1-(a/x)b, where bZ£1. This distribution law is often used for modelling both natural and man-made disaster data. For the Pareto law the cumulative sum of losses increases with time as ta, where a=1/b>1. In this case, the process is fully stationary, and the tendency to the non-linear growth is caused by an increase of probability of realisation of a huge disaster with time. The regime of non-linear increase of losses should saturate at some time moment because of practical limitation of possible loss size. Methods of evaluation of saturation parameters are presented and obtained results are discussed in connection with the social and economic situation in different regions. Besides, it was shown that after proper normalisation by size of the population and by per capita income the losses have a tendency to decrease with the level of social and economic development. Thus, in contrast with the wide-spread opinion, the regime of losses from natural disasters is compatible with conception of the sustainable development of society, moreover, it can be considered as an example of realisation of this conception. |
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