Quake alters earth's balance
The quake that struck northern Japan on Friday not only violently shook the ground and generated a devastating tsunami, it also moved the coastline and changed the balance of the planet.
Global positioning stations closest to the epicentre jumped eastward by up to 13 feet.
Japan is “wider than it was before,” said Ross Stein, a geophysicist at the United States Geological Survey.
Meanwhile, Nasa scientists calculated that the redistribution of mass by the earthquake might have shortened the day by a couple of millionths of a second and tilted the Earth's axis slightly.
That part of Asia, to the surprise of many who look at the geological map, sits on the North American tectonic plate, which wraps up and around the Pacific. In Friday's collision what geologists call a subduction zone the Pacific plate dives under the North American plate.
In the same way, the North American plate buckles, and the eastern part of Japan is slowly pushed to the west. But when the earthquake, which occurred offshore, released the tension, the land jumped back to the east.
As it unbuckled, a 250-mile-long coastal section of Japan dropped in altitude by two feet, which allowed the tsunami to travel farther and faster onto land, Dr. Stein said.
The quake also shifted the "figure axis" of the Earth, which is the axis that the Earth's mass is balanced around.
Earlier great earthquakes also changed the axis and shortened the day.