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bonitahi
03-01-2010, 07:16 PM
"Chilean Quake Likely Shifted Earth’s Axis, NASA Scientist Says"

March 1 (Bloomberg) -- "The earthquake in Chile on Feb. 27 probably shifted the Earth’s axis and shortened the day, a National Aeronautics and Space Administration scientist said. The axis about which the Earth’s mass is balanced should have moved by about 8 centimeters or 3 inches."

Shortened the day? I take that to mean that we all get to live longer now- or at least die later. Maybe we can squeeze in an extra Yankee game or whatever :)

Is that likely or even possible that the earth's axis moved that much?

Simplicio
03-01-2010, 07:21 PM
You think NASA is lying?

Squink
03-01-2010, 07:42 PM
For the Indonesian Quake: (http://www.jpl.nasa.gov/news/news.cfm?release=2005-009)January 10, 2005
Gross and Chao have been routinely calculating earthquakes' effects in changing the Earth's rotation in both length-of- day as well as changes in Earth's gravitational field. They also study changes in polar motion that is shifting the North Pole. The "mean North pole" was shifted by about 2.5 centimeters (1 inch) in the direction of 145 degrees East Longitude. This shift east is continuing a long-term seismic trend identified in previous studies.

They also found the earthquake decreased the length of day by 2.68 microseconds. Physically this is like a spinning skater drawing arms closer to the body resulting in a faster spin. The quake also affected the Earth's shape. They found Earth's oblateness (flattening on the top and bulging at the equator) decreased by a small amount. It decreased about one part in 10 billion, continuing the trend of earthquakes making Earth less oblate.
More from Dr. Gross at JPL:
"The length of the day changes about a millisecond over the course of a year," says Gross. "It gradually increases in the winter, when Earth rotates more slowly, and decreases in the summer. There are also longer patterns of changes in the length of day that last decades, even centuries."

All Days Are Not Created Equal (http://www.jpl.nasa.gov/news/features.cfm?feature=15)

kunilou
03-01-2010, 07:51 PM
To give you a sense of perspective, according to the article (http://www.irishtimes.com/newspaper/world/2010/0302/1224265432876.html) it shifted the axis by about 3 inches. The Earth's diameter is almost 8,000 miles. The quake also shortened the day by about 1.26 millionths of a second.

By contrast, a quartz wristwatch is accurate to about a half-second per day (http://www.economicexpert.com/a/Quartz:clock.htm).

Sapo
03-01-2010, 08:01 PM
You think NASA is lying?
Well, after the whole moon lan... never mind.

Harmonious Discord
03-01-2010, 08:54 PM
I hope I'm farther south now. With my luck I shifted north.

bonitahi
03-01-2010, 10:14 PM
But, if the earth's axis tilted three inches,
as the Bloomberg article states,
wouldn't we humans tend to tilt somewhat?
Ensuing ramifications in human relationships
and architectural engineering?

bonitahi
03-01-2010, 10:27 PM
Skuink..."Gross and Chao"

That just sounds funny, sorry:)
"oblateness" is cool, though.

But seriously...3"?
A change of 3 inches sounds really big to me!

Blake
03-01-2010, 10:27 PM
"The length of the day changes about a millisecond over the course of a year," says Gross. "It gradually increases in the winter, when Earth rotates more slowly, and decreases in the summer.

So the Northern hemisphere and southern hemisphere are rotating at different speeds.

Man, that must generate some torque.

bonitahi
03-01-2010, 10:35 PM
So the Northern hemisphere and southern hemisphere are rotating at different speeds.

Man, that must generate some torque.

Picture that. Whew!

bonitahi
03-01-2010, 11:13 PM
Back to the OP.
What about the larger quake in Haiti? Did that alter the earth's axis? In what direction?
The same or opposite of the Chilean quake? Do they balance the normal axis out?

As we all know there are many earthquakes per day in this world. Are they cumulatively moving the axis in a particular direction? Is there cause for concern because of them?

What would be the consequences if the axis altered by one or two percent...or more, because of earthquakes?

garygnu
03-01-2010, 11:24 PM
Back to the OP.
What about the larger quake in Haiti? Did that alter the earth's axis? In what direction? ...
FYI, the Chile earthquake release about 500 times (http://www.thestar.com/news/world/article/772765--why-chile-dodged-haiti-style-ruin) more energy than the Haiti earthquake. Haiti was worse on the human loss and destruction scale.

bonitahi
03-01-2010, 11:50 PM
"Haiti was worse on the human loss and destruction scale."

I know, much worse. It is so sad. And was much more disastrous.

But, did that quake alter the earth's axis to the extreme of the Chilean quake?

DrFidelius
03-02-2010, 06:32 AM
No, the Haiti quake was much weaker, just closer to the surface, which is one reason it caused more damage.

SenorBeef
03-02-2010, 07:24 AM
But, if the earth's axis tilted three inches,
as the Bloomberg article states,
wouldn't we humans tend to tilt somewhat?
Ensuing ramifications in human relationships
and architectural engineering?

I'm not quite sure of the cause of your misunderstanding, but having the Earth's axis rotate by 3 inches wouldn't affect the way things lean or anything like that. When we talk about the tilt, we're talking about the angle of the planet (from pole to pole) relative to the ecliptic on which it travels around the sun. It's currently about 23.5 degrees, as this picture (http://pauldeanno.com/wp-content/uploads/2009/08/earth_axis_0821.jpg) shows. We're either 3 inches more or less tilted relative to the ecliptic now (not sure which it is), so instead of a 23.5 degree tilt we're at (again if we're talking about 3" of increased tilt) 23.50000000000000000000000000000000000000001 degrees (number made up).

Pasta
03-02-2010, 07:50 AM
But, did [the Haiti] quake alter the earth's axis to the extreme of the Chilean quake?
I would suspect that the nature of the quakes is rather important here. To change the rotational speed of the earth, you need to move mass either toward or away from the rotation axis. The Haiti quake occurred along a strike-slip fault, where two plates move primarily laterally alongside one another with very little next vertical motion. The Chilean quake occurred along a thrust fault, in which one landmass burrows under another. The latter would result in more significant changes in the earth's moment of inertia.

Grey
03-02-2010, 08:10 AM
As we all know there are many earthquakes per day in this world. Are they cumulatively moving the axis in a particular direction? Is there cause for concern because of them?Seeing how we've survived earthquakes (and bigger ones than this) for 10,000 years I think we can safely say no.

Mangetout
03-02-2010, 08:12 AM
So the Northern hemisphere and southern hemisphere are rotating at different speeds.

Man, that must generate some torque.

I'm pretty sure we had someone here a while back who argued that the two hemispheres were rotating in opposite directions, but I can't find the thread. (It wasn't BZ00000, who thought that time would run backwards if the Earth's spin was reversed (http://boards.straightdope.com/sdmb/showthread.php?t=140878))

Munch
03-02-2010, 08:30 AM
So the Northern hemisphere and southern hemisphere are rotating at different speeds.

Man, that must generate some torque.

I caught that as well. Any idea what that guy is on about? Can we take the rest of his comments seriously with a flub like that? I'd say that if I caught the error, it's pretty egregious...

Squink
03-02-2010, 09:04 AM
(again if we're talking about 3" of increased tilt) 23.50000000000000000000000000000000000000001 degrees (number made up).

3" over 6371 km (radius) is 6.85 × 10^-7 degrees or 0.0025 arcseconds.

That figure is just under the resolution limit of the Keck interferometer (http://en.wikipedia.org/wiki/W._M._Keck_Observatory), 5 milliarcseconds.

Freddy the Pig
03-02-2010, 09:16 AM
I caught that as well. Any idea what that guy is on about? Can we take the rest of his comments seriously with a flub like that? I'd say that if I caught the error, it's pretty egregious...I'm sure that by "winter" he means northern hemisphere winter. In other words, the whole globe rotates more slowly in January and more quickly in July. There's no torque.

74westy
03-02-2010, 09:58 AM
When we talk about the tilt, we're talking about the angle of the planet (from pole to pole) relative to the ecliptic on which it travels around the sun.

That's not the way I read Squink's link (http://www.jpl.nasa.gov/news/news.cfm?release=2005-009) (say that three times fast).

NASA scientists using data from the Indonesian earthquake calculated it affected Earth's rotation, decreased the length of day, slightly changed the planet's shape, and shifted the North Pole by centimeters. The earthquake that created the huge tsunami also changed the Earth's rotation.

My emphasis.

This of course refers to the Indian Ocean quake but the kunilou's link (http://www.irishtimes.com/newspaper/world/2010/0302/1224265432876.html) suggests that we're talking about the same thing.

SenorBeef
03-02-2010, 10:36 AM
What does it mean by "shifted the north pole"? Does that mean the center of the magnetic pole changed which chunk of land it's on, or that the physical location of the north pole relative to the ecliptic has shifted as a natural consequence of very slight change in tilt? You may be right, but it sounds like we may be describing the same issue differently.

Colophon
03-02-2010, 11:51 AM
By contrast, a quartz wristwatch is accurate to about a half-second per day (http://www.economicexpert.com/a/Quartz:clock.htm).

Cheap crap quartz wristwatches, maybe. My digital wristwatch rarely gains or loses more than a second per month (and it's not a fancy radio controlled one or anything like that).

bonitahi
03-02-2010, 12:27 PM
Do the locations of the poles change?

74westy
03-02-2010, 12:50 PM
What does it mean by "shifted the north pole"? Does that mean the center of the magnetic pole changed which chunk of land it's on, or that the physical location of the north pole relative to the ecliptic has shifted as a natural consequence of very slight change in tilt? You may be right, but it sounds like we may be describing the same issue differently.

You're right that, based on a dumbed down news report, we can't be sure what's meant. Nevertheless, I took it to mean that the geographic pole moved to a chunk of land 3" from where it was.

The "mean North pole (http://www.jpl.nasa.gov/news/news.cfm?release=2005-009)" was shifted by about 2.5 centimeters (1 inch) in the direction of 145 degrees East Longitude. This shift east is continuing a long-term seismic trend identified in previous studies.

I don't know if that makes sense or not but the picture in my mind that same old figure skater only this time she just pulls in one arm. That would decrease her moment of inertia but also change her centre of gravity and therefore move her axis of rotation.

YogSothoth
03-02-2010, 12:57 PM
Do they have to recalculate everything about the earth's rotation and stuff whenever a big quake like this hits? I imagine that for little things like angle of a building, strength of a bridge, they don't have to do much adjusting, but if astronomers are using some base earth measurement to look at stars which are light years away, would a tilt of a few inches make a difference?

wolfstu
03-03-2010, 12:52 AM
Do they have to recalculate everything about the earth's rotation and stuff whenever a big quake like this hits? I imagine that for little things like angle of a building, strength of a bridge, they don't have to do much adjusting, but if astronomers are using some base earth measurement to look at stars which are light years away, would a tilt of a few inches make a difference?They do -- so do people trying to calculate the positions of satellites. Fortunately, the International Earth Rotation Service (http://www.iers.org/sid_34B234F7016BD2D50164E112D2405FE2/IERS/EN/IERSHome/home.html?__nnn=true) provides tables of the necessary corrections. It's not just earthquakes -- the Earth wobbles and shifts slightly all the time, due to external gravitational influences and internal shifts in the Earth's mass distribution. but we're talking small fractions of a degree.

BetsQ
03-03-2010, 10:06 AM
Do the locations of the poles change?

There are two sets of poles - the geographic poles and the magnetic poles. The magnetic poles certainly drift. Here's a map (http://web.archive.org/web/20070605175632/http://www.physics.sfasu.edu/astro/img/northpoledrift.gif)of where the north magnetic pole has been recently.

Freddy the Pig
03-03-2010, 10:48 AM
The geographic poles move also, and by a lot more than three inches--see the Chandler wobble (http://en.wikipedia.org/wiki/Chandler_wobble). Note that this is actual realignment of the axis of rotation relative to the stars, not surface movement due to plate tectonics or shifting ice.

Cat Whisperer
03-03-2010, 12:28 PM
I caught that as well. Any idea what that guy is on about? Can we take the rest of his comments seriously with a flub like that? I'd say that if I caught the error, it's pretty egregious...
Aw, I thought we were on our way to the science in "The Core" become accurate. :(