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NZ engineers study tsunami damage in Java - 31/07/2006

A group of New Zealand engineers and scientists has gone to Indonesia to study the impact of the recent tsunami in Java on buildings and other structures.

Led by earthquake engineer Jim Cousins of GNS Science, the team will work with Indonesian colleagues to collect information on how water depths and flow speeds affected structures as the tsunami waves travelled inland.

The information will be valuable for engineers and risk modellers in New Zealand. It will be particularly useful for refining inundation and damage models developed in a report on New Zealand’s tsunami hazards, commissioned by the Ministry of Civil Defence and Emergency Management in 2005.

The tsunami struck coastal districts in western and southern Java on 17 July, killing hundreds of people. Initial reports were of waves about 2m high. Scientists have subsequently learned that the waves were over 4m high.

The 10-day mission is being funded by the Earthquake Commission and the Foundation for Research Science and Technology. It involves three scientists from GNS Science and one from the National Institute of Water and Atmospheric Research (NIWA).

Tsunami scientist Gaye Downes, of GNS Science, said the tsunami wave heights in Java were comparable to what had occurred several times in New Zealand in the last 160 years. Similar wave heights might be expected in the future as a result of an undersea earthquake in distant parts of the Pacific, or near the New Zealand coast.

“The tsunami in Java was not so large that it destroyed everything in its path. The partly demolished structures it left behind will provide valuable information for engineers and risk modellers.”

Ms Downes said another factor that made the mission valuable, was the fact that the offshore earthquake that caused the tsunami was not felt strongly on the island of Java. “This means there was hardly any earthquake damage to buildings and other structures. Damage was due solely to the tsunami.”

Ms Downes said there was a worldwide shortage of in-depth information about the engineering impacts of tsunamis. The visit would address that gap and complement Japanese and American tsunami reconnaissance teams in Java, who are mapping the heights of the tsunami waves along the coast and gathering information on the geological and social impacts.

It is fortunate that engineering geologist Dick Beetham, of GNS Science, who is fluent in Indonesian and in Java on a post-earthquake recovery project funded by the New Zealand government’s overseas aid agency, NZ Aid, is able to join the team to help with the reconnaissance