Earthquake shortened days, shifted earth’s axis, moved Japan 13 feet
by Mary Elizabeth Dallas
Originally posted March 15, 2011
Experts say the March 11th earthquake in northern Honshu, Japan shortened the length of each Earth day, shifted the Earth’s axis and pushed Japan about 13 closer to North America, reports the U.S. National Aeronautics and Space Administration (NASA). “Don’t worry,” NASA says, “you won’t notice the difference.”
The USGS updated the magnitude of the recent earthquake in northern Honshu, Japan, to 9.1 from the previous estimate of 8.9. Independently, Japanese seismologists have also updated their estimate of the earthquake’s magnitude to 9.1. This magnitude places the earthquake as the fourth largest in the world since 1900 and the largest in Japan since modern instrumental recordings began 130 years ago, according to the U.S. Geological Survey (USGS).
Using a USGS estimate for how the fault responsible for the earthquake slipped, research scientist Richard Gross of NASA’s Jet Propulsion Laboratory in Pasadena performed a preliminary theoretical calculation of how the earthquake affected the Earth’s rotation. His 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 (a microsecond is one millionth of a second).
The calculations also show the Japan quake should have shifted the position of Earth’s figure axis (the axis about which Earth’s mass is balanced) by about 6.5 inches, towards 133 degrees east longitude. This shift in Earth’s figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth’s axis in space. NASA says only external forces such as the gravitational attraction of the sun, moon and planets can do that. Both calculations will likely change as data on the quake are further refined, NASA adds.
The 9.1 magnitude quake also shifted Eastern Japan towards North America by about 13 feet, and sank Japan downward by about two feet. As Japan’s coastline sunk, the tsunami’s waves surged in.
“Earth’s rotation changes all the time as a result of not only earthquakes, but also the much larger effects of changes in atmospheric winds and oceanic currents,” he said. “Over the course of a year, the length of the day increases and decreases by about a millisecond, or about 550 times larger than the change caused by the Japanese earthquake. The position of Earth’s figure axis also changes all the time, by about 1 meter (3.3 feet) over the course of a year, or about six times more than the change that should have been caused by the Japan quake.”
Gross said the changes in Earth’s rotation and figure axis caused by earthquakes should not have any impacts on our daily lives. “These changes in Earth’s rotation are perfectly natural and happen all the time,” he said. “People shouldn’t worry about them.”
Mary Elizabeth Dallas is based in New York City, New York, United States of America, and is Anchor for Allvoices