# Japan's earthquake and the Earth's axis

I've been hearing a lot lately about how Japan's massive earthquake moved the Earth or changed its axis by 1°-4°.

I personally feel that this is not possible, but I don't have nearly enough knowledge to refute it.

Is this possible? Why or why not?

• Discussed on physics.SE shortly after the event: How can earthquakes shift the earth's axis?. It is perfectly possible with the right understanding of what is meant by "shift the axis". Mar 30, 2011 at 21:47
• This is actually the true answer I was looking for! Thank you very much. Apr 1, 2011 at 1:02

This is actually pretty interesting. If you consider that figure skaters can change their rotation by adjusting the placement of their body mass (e.g. their arms), it is apparent that a simple geometry change can affect rotation.

After the Feb 2010 earthquake in Chile, Nasa released this press release:

http://www.jpl.nasa.gov/news/news.cfm?release=2010-071

[the Chile] quake should have shortened the length of an Earth day by about 1.26 microseconds...the quake should have moved Earth's figure axis by 2.7 milliarcseconds

So it seems it is possible, but perhaps not in the magnitude that you quote in your question.

• Thank you. My main argument was that if it indeed was true, it couldn't be by 4°. I feel like 4° would have some incredibly drastic effects. Mar 30, 2011 at 17:07
• @Vian -- Why do ytou believe that 4 degrees would have a drastic affect? Mar 30, 2011 at 17:55
• @Russell, maybe "drastic" wasn't the right word but I feel like 4 degrees would result in some very noticeable climate changes. Mar 30, 2011 at 18:15

Richard Gross, of NASA's Jet Propulsion Laboratory on the Japanese Earthquake:

According to a calculation I did [...] the days should have gotten shorter by about 1.8 microseconds. That's 1.8 millionths of a second.

...

the mass of the Earth is not balance about its rotation axis, and so it wobbles as it rotates, just like an out-of-balance tire on your car vibrates as it rotates. And it's that axis about which the mass is balanced is what shifted during this earthquake. The earthquake rearranges the mass of the Earth, and therefore the figure axis moved by about six-and-a-half inches.