The magnitude 9.0 earthquake that struck Japan March 11, 2011 may have slightly shortened the length of each Earth day and shifted its axis. Using a U.S. Geological Survey estimate for how the fault responsible for the earthquake slipped, a NASA research scientist applied a complex model to perform a preliminary theoretical calculation of how the Japan earthquake — the fifth largest since 1900 — affected Earth’s rotation. The calculations indicate that by changing the distribution of Earth’s mass, the Japanese earthquake should have caused Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds.