A decade has passed since a massive earthquake in Sumatra caused a tsunami that led to the deaths of hundreds of thousands of people.
As the anniversary approaches, seismologists are reflecting on the lessons learnt and improvements made, and look to obstacles ahead.
On December 26, 2004, the region lacked a co-ordinated Indian Ocean tsunami warning system, and awareness of tsunamis among the general public was low.
Now, education, communication and infrastructure have improved to better deal with such a disaster.
An earthquake is "an emerging rupture of crust", says Daniel Jaksa, co-director of the Joint Australian Tsunami Warning Centre.
"In this case, it started south of Banda Aceh and finished just near the area of Myanmar," he says.
About 230,000 people were killed by the tsunami, with coastlines in 12 countries devastated, including Indonesia, Sri Lanka, India, Maldives, Thailand, Myanmar, Malaysia, Somalia, Tanzania, Seychelles, Bangladesh and Kenya.
The extensive rupture produced the equivalent of two million atomic blasts of energy being released over 10 minutes across 1200km of the tectonic plate boundary, Jaksa says.
Such a consequence does not bode well for people living on coasts near where one tectonic plate slides under another, which is the typical point where tsunamis are generated.
"If an earthquake occurs under your feet and you're on the coast, then a tsunami's upon you in very short time frames - 10 to 15 minutes," Jaksa, of Geoscience Australia, says.
"That's how long it takes for us to analyse an earthquake and issue a tsunami warning."
Although earthquakes are unpredictable, he says people away from the epicentre have time to receive a warning and act.
"People who feel an earthquake on the coast shouldn't be hanging around on the coast. They should be going inland and uphill ... as quickly as possible. That means run. Don't drive a car," Jaksa says.
In 2004, the Joint Australian Tsunami Warning Centre monitored 33 stations, all but one of which were in Australia.
Now, seismologists monitor more than 300 stations worldwide.
Even though the technology of seismometers hasn't changed for decades, communication has.
In the 1950s, seismic observatories used morse code to share wave arrival times.
"We're now able to look at seismic data at 40 samples a second from 300 stations, and with three channels to a seismometer, in real time," Jaksa says.
In 2007, the warning centre also began monitoring earthquakes 24 hours a day, as opposed to having a Geoscience Australia seismologist on call.
In the Indian Ocean, the centre can locate and calculate the magnitude of an earthquake within 10 minutes of its initial rupture. A tsunami warning is issued two to five minutes later.
"The problem is, earthquakes rupture over time and space, so the magnitude 9.1 Sumatra actually ruptured for 10 minutes, and that's why we talk about preliminary magnitudes and preliminary locations," Jaska says.
One of the biggest realisations following the 2004 Indian Ocean tsunami and 2011 Japan tsunami (which led to the Fukushima nuclear disaster), is that uncertainty remains about what sort of faults can generate what size earthquakes, Jaksa says.
There is also the problem of complacency.
"We have always known that there's a tsunami threat from subduction zones ... the problem is they're so infrequent, these events, that the general community tends to ignore it," he says.
Jaksa is passionate about maintaining awareness of tsunamis or, rather, institutionalising the knowledge about them.
Improvements in this area have been made in Indian Ocean countries, with evacuation centres having been built and warning systems in place in beachside suburbs.
But complacency must still be fought.
"In Australia, we're not likely to get the tsunamis that we see in Japan and Indonesia, but we will get ones that you saw in Thailand or Malaysia," Jaksa says.
Share
