This paper reports on the 3-day reconnaissance visit to the damaged sites of Magnitude 6.9 Chuetsu Earthquake in Niigata, Japan. The damage characteristics of about thirty highway bridges visited is described in detail. The damages to bridges were not extensive and less severe than witnessed in the Hyogo-ken Nanbu Earthquake of 1995. The main reason is that there are not many bridges in the areas that experienced high intensity earthquake ground motions. It was observed that bridges, which have been seismically retrofitted, performed satisfactorily without sustaining severe damage. It is vital that bridges designed to older design specifications should be retrofitted as soon as practicable. There was not enough evidence to confirm that bridges designed and constructed to the current specifications have performed well under the near field strong earthquake.
Paper P16: [Read]
The role of the Fire Departments in Kobe and Tokyo after earthquakes is reviewed following the 1995 Great Hanshin-Awaji (Kobe) and other earthquakes and subsequent fires. In Japan effort has been focused on providing fire-fighting water supplies after an earthquake including the purchase pumping vehicles and hose-layers and the planning and installation of additional underground water cisterns. Upgrading water supplies should be considered in New Zealand. Both Fire Departments have developed computer models to predict fire spread and to allocate fire-fighting resources efficiently. Despite the large amount of resources available in Japan they are insufficient to fight all the predicted fires. This situation is similar to that faced by a city like Wellington. Analysis of the rescue efforts after the Kobe earthquake has resulted in a change of focus from expecting the Fire Department to rescue people trapped in buildings to providing more resources to aid the rescue efforts of local volunteers This is an approach which may be appropriate in New Zealand.
Paper P17: [Read]
Many parts of the earthquake loss modelling process are subject to uncertainty, including such very basic inputs as the magnitude of the earthquake (for which the uncertainty is typically ±0.3), the location of the earthquake (±5 km?), and often the mechanism of the rupture process (strike-slip, reverse, etc). The above uncertainties alone can give rise to uncertainty factors of 2 to 3 in loss estimates, under favourable conditions, increasing to factors of 1000 to 10,000 under unfavourable conditions. Favourable conditions are high intensities and large magnitudes, unfavourable conditions are low intensities and small magnitudes. The reasons for this are explained. In order to achieve reliable loss estimates the results of many thousands of scenarios may need to be averaged, with the input parameters being varied from one scenario to another. Use of a suitably randomised synthetic catalogue of earthquakes is one way of achieving this. Applying a 100,000-year catalogue to the whole of the present building asset of New Zealand suggests that the mean return period for a loss exceeding $1 billion is just 60 years. The most recent earthquake capable of generating such a loss was the Hawke’s Bay earthquake of 1931.
Paper P18: [Read]