How It Works

Did the 2011 quake in Japan shorten the days on Earth?

Yes, but you’re unlikely to notice. Every day is now 1.8 microseconds shorter, according to NASA. The Japan earthquake made Earth spin slightly faster by changing its rotation around an imaginary line called the figure axis. The Earth’s mass is balanced around the figure axis, and it wobbles as it spins. That wobble naturally changes one metre (3.3 feet) a year due to moving glaciers and ocean currents. The 2011 Tohoku earthquake moved the ocean bed near Japan as much as 16 metres (53 feet) vertically and 50 metres (164 feet) horizontally – that’s the equivalent horizontal distance to an Olympic swimming pool! The shifting ocean bed increased Earth’s wobble around the figure axis by 17 centimetres (6.7 inches). As the wobble grew, Earth sped up its rotation. It’s the same principle as when a figure skater pulls their arms closer to their body in order to spin faster.