First video of an earthquake fault cracking has revealed another surprise

A first-of-its-kind video showing the ground cracking during a major earthquake is even more remarkable than previously thought. It not only captures a ground motion never caught on video before but also shows the crack curving as it moves.

This curvy movement has been inferred from the geological record and from "slickenlines" — scrape marks on the sides of faults — but it had never been seen in action, geophysicist Jesse Kearse, a postdoctoral researcher currently at Kyoto University in Japan, said in a statement.

"Instead of things moving straight across the video screen, they moved along a curved path that has a convexity downwards, which instantly started bells ringing in my head," Kearse said, "because some of my previous research has been specifically on curvature of fault slip, but from the geological record."