Everyone who read the news on Wednesday heard about the major 8.5 magnitude earthquake that struck just off the south west coast of Sumatra, Indonesia, right in the Indian Ocean. It occurred at 8:38 PM GMT, and was followed by another at 8.2 magnitude aftershock at 10:43 PM GMT. Though it was an aftershock, it was clearly not that much weaker, and by comparison was really a second earthquake. They were both felt in nearby Sumatra, as well as India, Singapore, Thailand, Myanmar and Bangladesh.
Because the earthquakes struck under the seabed, it immediately raised fears of the possibility of a tsunami. Almost every coastal resident in each of these countries has terrible memories of the tsunami that devastated the west coastal regions of Thailand, Myanmar, and the northern
regions of Sumatra. As soon as the shaking finished in the morning tsunami warnings rung out. People in the city of Banda Aceh, at the northern tip of Sumatra, started to flee to higher ground before local officials even had a chance to notified the media and issue warnings. The panic had struck, hospitals emptied right away and people took any form of transportation they could find.
Since the mammoth tsunami and earthquake that occurred in the exact same region in 2004, as well as the devastating tsunami and earthquake that hit Japan last year, there was certainly a historic precedent that justified the fear that another giant wave could strike again. In recent years these two types of disasters seem to be symbiotic, particularly in Asia. In fact by the response that one saw in the news this morning, the biggest concern was whether there will be an tsunami, and that rescuing people from collapsed buildings and rubble no longer has the same importance that it used to.
In the end authorities from each of the affected countries withdrew their warnings after several hours when it became clear that there were no giant waves.
Fears were justified though. As it turns out, there was a tsunami, according to Emile Okal, geophysicist at Northwestern University. He was quoted as saying "There was a tsunami, but the waves were just below 1 meter." Some people may roll their eyes at this measurement. I believe some kids might have even cannon-balled bigger tsunami’s in a swimming pool.
In the end there was no serious damage, and by the afternoon the citizens of Banda Aceh descended from the hills into their homes, to clean up the mess left by the sea-quake. The fact that this turned out to be much less of a disaster than in the past was due to some important factors. Since 2004 all of these regions were better prepared with improved emergency response systems, improved warning systems, and stronger infrastructure and building standards. Also apparently the type of earthquake that struck was a strike-slip earthquake, which involved the tectonic plates sliding against each other. It would have been much more devastating if it involved a vertical collision of plates.