Pacific Scoop

NZ scientists learn lessons from Samoa tsunami

Press Release – NIWA

A team of NZ scientists say the results of their field work after the Samoa Tsunami are of interest internationally and here in New Zealand. NZ scientists learn lessons from Samoa tsunami

A team of NZ scientists say the results of their field work after the Samoa Tsunami are of interest internationally and here in New Zealand.

The team from the National Institute of Water & Atmospheric Research (NIWA) and GNS Science spent nearly two weeks in the field: six days in American Samoa and seven days in Samoa. In Samoa, the NIWA / GNS Science delegation was part of a UNESCO–IOC International Tsunami Survey Team.

This project was unique in that it involved a coordinated team of international scientists who sought to collect evidence across a wide spectrum of the tsunami’s impact on communities, individuals, infrastructure, and the environment.

“We broke new ground for the disaster loss assessment research community. Our results illustrate an effective use of cutting edge field methods,” says NIWA’s Dr Shona van Zijll de Jong.

The aim of the visit was to gather a wide range of information to help Samoa, and other Pacific Islands including New Zealand, become better prepared to cope with future disasters.

Samoa, like New Zealand, is vulnerable to a wide range of natural disasters such as earthquakes and tsunamis, cyclones and floods. Samoa’s recent experience with natural disasters, such as the two closely-spaced cyclones in 1990 and 1991, have assisted in better preparing many local communities to withstand the impact of such natural hazards and to plan for the future.

Preliminary results from their survey of the physical and human effects of the Samoa tsunami have direct relevance for New Zealand say the scientists involved.

Size of tsunami
The Samoa tsunami consisted of two to three significant waves; the second wave was said by witnesses to be larger. The delay between the earthquake and the arrival of the first wave was about 10 minutes in Samoa and 20 minutes in American Samoa.

The maximum height reached by the tsunami on the land was 14 metres above mean sea level in Samoa and 10 metres in American Samoa. The furthest inland the waves reached was over 700 metres from the shore.

“This size of tsunami is also possible for New Zealand, equivalent to about a one-in-500 year event for the most populated parts of New Zealand,” says GNS Science spokesman John Callan.

Building damage
Buildings sustained varying degrees of damage. The importance of reinforcement was very clear – traditional light timber buildings were typically completely destroyed at an inundation depth of 1.5m or higher, whereas adding minimal reinforced-concrete columns reduced the damage levels significantly.

Building damage was correlated with water depth, structural strength, shielding, condition of foundations, quality of building materials used, quality of workmanship, and adherence to the building code.

It was also very clear that plants, trees, and mangroves reduced flow speeds and depths over land – leading to greater chances of human survival and lower levels of building damage.

“The same thing will be true in New Zealand as in Samoa: solidly constructed buildings which are appropriately located will survive much better than flimsy buildings right on the beach,” says Dr Stefan Reese of NIWA.

“It’s also clear that practices such as flattening sand dunes or removing beach vegetation would increase the potential for tsunami damage.”

Community response
In Samoa, it was clear that community-based tsunami education activities had saved lives in some areas, while in others there was still some confusion about how to respond.

The impact of the tsunami may have permanently changed residential patterns in Samoa. “Many people are scared of the sea, and people are staying away from devastated villages” says Dr van Zijll de Jong.

“The sea has been a source of livelihood and identity for generations. The violence of the tsunami really shook them. Their sense of personal security and economic well-being is deeply shaken.”

The Government of Samoa is very supportive of communities that want to resettle further inland. However, the families that have moved inland are very aware of the challenges facing them in re establishing their communities, particularly with it now being cyclone season. There is a very strong social fabric in Samoa, through families, villages, religious organisations and right up into government at a local and national level. It is this strong social fabric that strengthens the local, cultural and economic features of the Samoan coastal communities and holds the basis for the resilience that allows people to more quickly recover from disasters says van Zijll de Jong.

The team also found that national and international response to the disaster had been extremely good. The interface between the Government of Samoa and in-coming international, regional and local humanitarian groups who had the capacity to respond to the disaster was impressive.

The team from NIWA and GNS Science was part of a UNESCO-IOC International Tsunami Survey team from New Zealand, Australia, Fiji, French-Polynesia, Italy, Japan, and the USA, in collaboration with teams from several ministries within the Government of Samoa.

The research report and methods are of interest to the local and international disaster loss assessment research community: New Zealand Ministry of Civil Defence and Emergency Management; the World Bank; United Nations Development Programme and Intergovernmental Oceanographic Commission (IOC) of UNESCO (United Nations Educational, Scientific and Cultural Organization)


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1 comment:

  1. John Delano, 4. December 2009, 21:09

    Originofquake Dec. 4 2009

    The mention of a 500 year event ,the 8.0 earthquake is an insult to the general population because it does not inform us of the meathod used in the calculation. Did the scientist in this article go and ask a couple of 1,000 year old men or women who happened to live on the Island what happened 500 years ago?

    The people on the island are scared and they should be. The scientist in this situation are 100 % wrong. The huge quake 8.0 could happen as often as 3 or 4 times a day. Not one person can say with absolute certantity what is going to happen.

    The science that the scientists are using is wrong. The Plate Tectonics Plate movement science and the buildup of stress or strain is not correct using this 100 year old science.

    These Vast trenches that are in the area of New Zealand go all the way to Fiji , then the trench makes a left turn to follow “The Wallace Line”, north of Australia , and then the trench continues with the Java-Sunda trench up to th Adaman sea area. That December 26 2004 horrible earthquake and Tsunami that killed 230,000 people is all related to what I am about to say , and it has nothing to do with the 500 year build up of stree or strain.
    Tsunami’s are important to understand how they formed and what is going on is another subject.
    We are discussing is why science is not advancing, and why we have not found a tenable theory to explain these earth processes, and abandon Plate Tectonics.

    The PLate Tectonic Explanation of the hot core boiling and moving the mantle like porage boiling in a pot on the stove is incorrect. The small fact that the inner core of planet earth has an inner core the revolves one revolution every 300-700 years faster then the upper mantle .cancels out the boiling porage arguement. The spinning inner core is disapating the heat of the core rising through the mantle like the spinning dish in your microwave oven. This spinning dish in the microwave oven is disapating the heat..
    These Islands next to these deep trenches is a disaster waiting to happen.
    I considered the people of Italy living on the Appenines mountains foolish due to the Appenines are not folded mountains ,but are rising “Ocean ridge” that happenes to be above sea level. The earthquakes in the mountains of Italy will continue at the same pace as the quakes along the 40,000 miles of ocean ridges.
    Listen to my brief discussion of what is going on. We have to go back 4.5 billions of years ago when our moon was formed:
    The idea that billions of years ago the formation of our moon created a hollow on 1/2 our planet after a collision with a huge planatary object. That collision caused the excavation of the hollow ,now filled with water and we call it the Pacific Ocean. This Ocean on 1/2 the planet earth fills avoid that has all the missing material to form our moon. The hollow was large enough to accumulate all the liquid water on the planet.
    After millions of years this water frooze solid. The earth had no atmosphere and the temperature was as cold as outer space.
    When the ice froze solid it rose. Whwn the semiliquid Mantle material returned under the ice to repair the damage , the ice rose. When the radioactive material expanded the mantle material under the ice it rose.
    It rose 18 miles high and was an asemetric [uneven] load on the surface of the planet earth. When the downward force toward the equator is large enough the mass will move toward the equator. This ia Albert Einstein’s physics , not mine.
    It had to move, to find equilibrium with no oceans billions of years ago, and therefore no tideal influences to slow down planet earth , the planet spun much faster and the revoluationary forces caused the ice to move. Embedded in the lithosphere the ice was the crust and the friction of the movement ,the heat of friction melted the land beneath the 18 mile high ice cap.

    The ice cap could only push the total crust over the earth in two big halves, and where they split the TRENCHES FORMED!

    This is true and correct in every detail. Your comments and questions will be answered if you e- mail me.
    John Delano