December 26, 2004. On this day, the worst tsunami in living memory pummeled Indonesia and shocked the world. The first tsunami to occur in the age of mobile camera phones, it was experienced by people all over the world through the shaky handheld videos that emerged of the catastrophe. The footage of the tsunami conveyed the ordeal through the eyes of the survivors, but it also had a practical benefit. Video footage enabled scientists to understand tsunamis more. Here's how.
Before the 2004 tsunami - which was a result of an earthquake in the Indian Ocean - the ways that scientists gathered information about tsunamis was done roughly and with a lot of estimation. Scientists would rely on measurements of the water marks on buildings with measuring tapes, examine the debris to guess how far it had traveled, and ask eyewitnesses questions about which direction the water came from, how quickly it moved, if there were any waves, and how deep the water became.
These methods, especially questioning eyewitnesses, are not particularly reliable, but they were the only tools that scientists could use at the time. As a result of this, there was little understanding about how tsunamis behaved, meaning that there was little to no warning before a tsunami hit land.
In the aftermath of the 2004 tsunami, videos filmed by tourists began emerging from Sri Lanka and Indonesia. Most of the videos were blurry and chaotic as people ran for their lives - but a few videos managed to capture the water moving inland as survivors filmed the disaster from high, safe places. In these videos, scientists can ascertain the depth of the water from footage of the water rising through the streets and buildings. They also survey the locations in the video, calibrating the perspective and the motion of the camera.
Access to such videos resulted in more precise measurements of how fast the water moved when it reached residential areas. When comparing this new information to that gathered using previous methods, it was revealed that eyewitnesses seriously underestimate the speed of the water by just looking at it. This information is highly valuable to scientists.
Another discovery made by the footage of tsunamis was that while normal waves slow down as they hit dry land, tsunami waves actually accelerate when they approach land. This was information that no eyewitness had ever noticed.
As smartphones became more advanced and widespread, by the time the 2011 tsunami hit Japan, scientists were able to gather more data about tsunamis than ever before. In order to obtain accurate data, scientists went back to the location where survivors filmed their videos and used a terrestrial laser scanner (LIDAR) to create a digital map of the landscape. Then they could superimpose the real life scan onto the video of the location under water to find out how fast the water moved.
Scientists could even isolate a piece of debris to determine its speed and the pattern of the flow of water, and how quickly a human would have to run to be out of danger's way. The scientists found out that in the event of powerful tsunamis like the 2011 tsunami in Japan, people would have to run as fast as Usian Bolt to outrun the tsunami, which is 27.8 miles per hour - the average adult runs at around 15 miles per hour.
The advent of video footage of tsunamis marked a change in the technology that could warn people about incoming tsunamis. The images from videos help scientists confirm the accuracy of the computer programs that predict when a tsunami will hit. Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys are another tool for warning of oncoming tsunamis, 60 of which are located in the world's oceans today.
By combining these two methods of prediction, as well as the data from seismometers, scientists have a much deeper understanding of tsunamis than they did twenty years ago. This means that they are more well-prepared to warn people of a potential tsunami - and save more lives.
If you happen to be unlucky enough to witness a tsunami, take a video of it (after ensuring your safety, of course). It will be more than a viral video for your Instagram feed - it could help scientists to save more lives.
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