Simon Day: The death toll could have been so much lower

The scale of the disaster caused by the Indian Ocean tsunami makes it difficult to analyse the event dispassionately. Nevertheless, it is only by understanding how and why a geological event led to human tragedy that we can learn to cope with future occurrences. It is true that there are some rare natural catastrophes against which we are defenceless, but there are many others whose consequences for human lives we can at least in part prevent or mitigate.

Perhaps the deepest tragedy of the Boxing Day tsunami lies in the one to three hours between the recording of the earthquake on the worldwide seismic network and the arrival of the tsunami waves on distant coasts, while their victims lived out the last hours of their lives all unawares. With less than an hour of warningand knowledge of what to do, most of those caught up in the disaster could have walked a mile inland to safety, and the death toll would have been in the hundreds rather than the tens of thousands.

Tsunami warning systems come in a variety of shapes and sizes. The basic elements are common to them all: a network of sensors to detect the waves or the phenomena that cause them; a communications network to warn the people who need to respond; and education to ensure that people know what to do when the warning reaches them. The warning system that could protect people living on the coasts of India, Sri Lanka and Thailand against tsunamis generated by earthquakes would be like the longest-established tsunami warning system of them all.

For 50 years, the Pacific Tsunami Warning System has used seismometers to record the earthquakes that cause most (but not all) tsunamis around the Pacific Ocean. When these occur, the system issues a series of tsunami watches and (once it is known that a wave is on its way) tsunami warnings. The hours that the waves take to travel across the ocean provide time to evacuate the coastal sites at risk.

The system isn't perfect - it is prone to false alarms and it does not protect well against tsunamis caused by submarine landslides or volcano collapses - but it is better than nothing. More recently, it has been improved by adding ocean floor pressure sensors to detect the tsunamis as they begin their journey from the subduction zones where most of them are produced.

Communication systems need to be tailored to their purpose, but in the age of e-mails and mobile phones, these are getting easier to provide. It is, of course, vital that the message gets through to the people on the coast, but even if only one official in a village has a mobile phone, that person can spread the warning.

Close to the tsunami source, this isn't necessary. Education alone saves lives. I have recently returned from research fieldwork in Papua New Guinea, during which my colleagues handed out leaflets produced after the 1998 Sissano tsunami disaster. These explained what people should do as soon as they felt an earthquake or the sea began to move: run for high ground or inland or, as a last resort, climb a tree.

As it turned out, these leaflets only reinforced what the people were already doing. Although these villages are among the least developed in the world, forethought and practical action by their inhabitants can make the difference between a natural event and a natural disaster.

Even before the events of 26 December, the historical record of tsunamis in the Indian Ocean (such as the last giant Sumatran earthquake in 1833) was such that the effort needed to implement a tsunami warning system in the region could have been justified. The best monument to the dead from this disaster would be to ensure that this effort is now made. The earth sciences provide better answers to natural catastrophes than Stoicism. Man is not powerless in the face of nature if he applies his intelligence and energy to the task.

Simon Day is an associate member of the Benfield Greig Hazard Research Centre, University College London, and is presently a visiting researcher at the University of California at Santa Cruz