On December 26, 2004, the worst tsunami disaster in living history took place across several countries including Thailand, caused by an earthquake in the Indian Ocean. More than 230,000 people were killed and 1.7 million displaced. To prevent tragedies like this in future, experts have researched the disaster, and determined what can be done to prevent similar tragedies in future.

DW: Professor Rhyner, looking back to the 2004 tsunami, why were so many lives lost in that particular disaster?

There are two main reasons for it. The first one was the infinite spatial extent of this disaster. We have no such a wide area, including several continents, in hardly any other disaster. And the second [reason] was the non-awareness of people. Hardly anyone knew what was going to happen, simply because this is a very rare disaster.

What has changed since 2004 in terms of being prepared for the impact of a disaster like that?

A lot has changed. First of all, very generally, the word "tsunami" has come to the minds of people. Many of us before 2004 didn't even know what a tsunami is, so just in general the awareness has grown. And a lot has been done in reconstruction. On a more technical level, a lot has been done with respect to early warning systems.

How does the technology of an early warning system actually work?

There is a whole range of technology involved in such a warning. First, you have to discover the source of the tsunami - which is in most cases an earthquake - so you need a seismometer. And then it is very important to transfer this data very quickly to a center where you can analyze it, mostly this is going via satellite. Then, you have to find out whether this earthquake will be able to initiate an ocean wave, or a tsunami. For this you need to do modeling, you need large computer capacity. Once you have decided that there is damage potential, that you might have a tsunami, you need people who write up this message and send it out. And in the end, you have to get it to the people.

Presumably that involves a lot of work with the local communities onsite?

Yes, there is something called the "last mile," when the warning has left the high-tech area and should reach the people. First of all, the people have to be aware that there is such a thing as a warning - otherwise people don't even know that there is a warning system. When people receive this warning, they have to accept it and understand it.

You find many people who think that such a big hazardous event is fate, it is sent by god, and they won't necessarily accept that kind of warning. So there may be lots of cultural obstacles you have to cross. Then, once people have accepted the warning, they have to know what to do, where to run and where to find shelter, so a city has to organize itself to be able to deal with the warning and react appropriately.

Thailand was one of the affected countries and the authorities there are said to be playing down the danger of a possible repeat of the tsunami, to not damage the tourist industry. Does that affect the implementation of early warning systems?

Yes. When it is played down, it affects the quality of safety. You don't have to go to Thailand to see this. My home country is Switzerland, and there we observed that in some cases, tourism directors tried to play down natural hazards - in this case, snow avalanches in the Alps.

But overall I think there has been a good development in the sense that people discover more and more the possibility of marketing safety. They don't try to play down the danger, but they say, "Yes it is there, and if you come to us we take care of these dangers, we have early warning systems, we will explain you the early warning systems for example on leaflets and so on." This is why putting in place an effective already warning system takes such a long time.

Has tsunami preparedness been taken into account in the reconstruction of destroyed areas?

I terms of reconstructing houses and infrastructure, yes, a lot has been done. But I would say that the overall results are a bit mixed. Not in the sense of speed - this has been good - but in the sense of how to protect against future tsunamis. After such an disaster you have an extreme amount of money available, which in many cases due to the mechanisms with which it was collected, also has to be spent very quickly. It would be better if more time would be taken until this money is spent, because if you have very little time, then you tend to rebuild the houses where you had them before, and this is not always the most appropriate.

At this time of the year, when many people are troubled by the memory of this terrible event, what would you tell them to ease fears that something like that could happen again?

The fear they have is a sign that awareness has grown. And when you are aware of such danger, then your risk is really reduced. So next time someone is traveling to Thailand and he sees the sea retreating, he knows that this is not a reason to go in and look for something in the sea, but rather a reason to run away. This is a lesson I think we have learned with this tsunami. So the fear we have is really a resource for reducing risks. This is the good message in all the bad.

Jakob Rhyner is the director of the Institute for Environment and Human Security at the United Nations University in Bonn, Germany. He holds a PhD in theoretical physics and is a member of numerous professional organizations and boards, including the Swiss Expert Group on Natural Hazards, and the Swiss Physical Society.