From Andrew Hammond
Christmas holidays tend to be a time of joy for many families around the world. However, this year’s festivities will also be tinged with great sadness for many as the world on Thursday (Dec. 26) marks the 20th anniversary of the devastating Boxing Day Tsunami.
Two decades on from the deadly waves, caused by a massive earthquake, that caused devastation in countries with Indian Ocean coastlines, scientific advances have improved our ability to forecast and provide warnings of dangerous tsunamis.
However, the economic and wider human costs of such natural catastrophes can never be completely eliminated. This was illustrated, for example, by the concern caused by a magnitude 7.0 earthquake this month about 55 miles off the coast of Eureka in California. The effects were felt from San Francisco to southern Oregon, sparking a tsunami warning affecting millions of residents. The alert was later canceled.
Tsunami warnings are relatively rare on the US West Coast but still more common than elsewhere in the country. However, some scientists predict the area might be overdue for a massive quake, and resulting tsunami, in the Cascadia Subduction Zone, an 1,100 km offshore fault that runs from northern California to southern British Columbia, and/or the San Andreas fault, which runs for 1,200 km through California.
Some scientists refer to this potentially huge natural disaster as “The Big One,” defined as an earthquake of magnitude 8.0 or higher on the Richter scale. Such an event could cause hundreds of billions of dollars of damage, and tens of thousands of deaths and injuries at the very least.
But even a disaster of that magnitude might still be dwarfed by the devastation caused by the 2004 Boxing Day Tsunami in the Indian Ocean. According to the EM-DAT global disaster database, it killed a total of 226,408 people in more than a dozen countries, and more than 1.5 million people were displaced.
The magnitude 9.1 earthquake that caused the tsunami was one of the biggest the world had seen since 1900. The epicenter was off the western coast of the Indonesian island of Sumatra. It was the longest fault line rupture ever observed, as the ocean floor opened up along a distance of at least 1,200 km between the India plate and Burma microplate.
The earthquake triggered the largest tsunami in the Indian Ocean for more than 700 years. The amount of energy it released was estimated to be equivalent to about 23,000 Hiroshima bombs. The huge waves it created, some more than 30 meters high, swept into several coastal nations, including Indonesia, Sri Lanka, India and Thailand.
Twenty years on, the silver lining amid the sadness of the upcoming anniversary is that our understanding of tsunami risks is now better. This means better forecasting, more effective warnings, and improved disaster-resistant construction techniques for more-resilient infrastructure.
In terms of warning systems, there were none in place in the Indian Ocean region in 2004. The picture has changed since then, with a regional system in place as part of an approximately 1,400-strong network around the world that generally reduces the delay in issuing a warning after a tsunami forms to just minutes.
Even with such improved warning systems, some communities still might not receive the alert in time. Indeed, had the present-day Indian Ocean warning system been in place in 2004, it is not certain it would have helped many of those among the first hit by the tsunami, especially in poorer communities lacking the benefit of modern digital technologies.
In part, this is why a significant proportion of tsunami casualties tend to happen before any official or technically based warnings can be delivered. This differs from some other natural hazards, such as hurricanes, which can be predicted further in advance and tend to cause fewer casualties.
However, for people more distant from the origin point of a tsunami, warnings can be very effective, including those transmitted through community communications. These can save many lives, with a key factor in success being the distribution of data rapidly, transparently, and hyper-locally, so that it is available in the best form, in the right place and as quickly as possible.
As warning systems improve, there are continuing debates about the enhanced exchange of data. This places an increasing amount of weight on improved forecasts. Such methods of predicting earthquakes in advance were once thought to be impossible, owing to the difficulty of calculating the motion of rocky mantle flows beneath the earth’s crust.
Thanks to increasingly sophisticated algorithms, however, it might now be possible to model this underground activity in more effective ways by creating a model of fault lines, consisting of millions of underground grid points, to ascertain where the underground stresses are strongest. This is a potential indicator of key earthquake trigger points.
However, even if forecasting technology and early warnings can fulfill their full longer-term potential, there is still a need for increasingly resilient infrastructure, given the devastation tsunamis can cause to physical geography.
Take the example of the province of Aceh in Indonesia, one of the areas worst-hit by the 2004 tsunami. Hundreds of thousands of homes were destroyed and about 3,000 hectares of land were washed away, destroying infrastructure such as roads, ports, and bridges.
More than 100,000 houses have been rebuilt there, according to the Indonesian government. –FP
