Big Quakes on Camera

December 05, 2008

What's a 8.4 magnitude earthquake feel like? Hard to convey over the Internet, but we have some exclusive footage here of a duo of  8.4 and 7.9 quakes as they rumbled through the island of Siberut, off the coast of Sumatra on Sept. 12, 2007. This is near a section of the same gigantic, super-active fault that gave is the Great Indian Ocean Tsunami and its monster megathrust quake. It's also a place that might be ready to unleash another such monster. The videos were taken by John Galetzka, a field geodesist, who was deploying GPS stations at the time these earthquakes struck, and supplied to Discovery Channel by Caltech seismologist Jean Philippe Avouac.

In the first part shown here Galetzka gives us an idea how the locals responded to the heavy shaking. People raced for the highest ground they could find -- a very wise decision even if no tsunami came. In places like Sumatra, where tsunamis can reach land just minutes after a quake, there is no better alarm system than a quake itself. Feel a jolt? Bolt!

Next we see how Galetzka is so caught up in recording the second 7.9 quake for science that he momentarily forgets about the danger of tsunamis. When he finds himself alone on the beach, self preservation kicks in and he follows the locals and heads for high ground. He even from higher and probably more stable ground (perhaps the reason he thought the later and lesser quake is more powerful -- since it was felt on a sandy beach).

Finally we see through Galetzka's eyes as he records the 8.4 quake.  Always the scientist, Galetzka tries to estimate the periods of the seismic waves and even lies down on the ground to get a better feel as the shaking subsides. In this video you can also see Galetzka's GPS equipment, in particular the solar panels in the background. The GPS stations he deployed help geoscientists study how the crust is being contorted in this very active part of the planet (for more on this see this slideshow).