Chile Earthquake May Have Shortened Days on Earth

**gunnut** · 02 Mar 10,, 23:59

Chile Earthquake May Have Shortened Days on Earth

SPACE.com Staff

SPACE.com Space.com Staff

space.com – Tue Mar 2, 10:00 am ET

The massive 8.8 earthquake that struck Chile may have changed the entire Earth's rotation and shortened the length of days on our planet, a NASA scientist said Monday.

The quake, the seventh strongest earthquake in recorded history, hit Chile Saturday and should have shortened the length of an Earth day by 1.26 milliseconds, according to research scientist Richard Gross at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"Perhaps more impressive is how much the quake shifted Earth's axis," NASA officials said in a Monday update.

The computer model used by Gross and his colleagues to determine the effects of the Chile earthquake effect also found that it should have moved Earth's figure axis by about 3 inches (8 cm or 27 milliarcseconds).

The Earth's figure axis is not the same as its north-south axis, which it spins around once every day at a speed of about 1,000 mph (1,604 kph).

The figure axis is the axis around which the Earth's mass is balanced. It is offset from the Earth's north-south axis by about 33 feet (10 meters).

Strong earthquakes have altered Earth's days and its axis in the past. The 9.1 Sumatran earthquake in 2004, which set off a deadly tsunami, should have shortened Earth's days by 6.8 microseconds and shifted its axis by about 2.76 inches (7 cm, or 2.32 milliarcseconds).

One Earth day is about 24 hours long. Over the course of a year, the length of a day normally changes gradually by one millisecond. It increases in the winter, when the Earth rotates more slowly, and decreases in the summer, Gross has said in the past.

The Chile earthquake was much smaller than the Sumatran temblor, but its effects on the Earth are larger because of its location. Its epicenter was located in the Earth's mid-latitudes rather than near the equator like the Sumatran event.

The fault responsible for the 2010 Chile quake also slices through Earth at a steeper angle than the Sumatran quake's fault, NASA scientists said.

"This makes the Chile fault more effective in moving Earth's mass vertically and hence more effective in shifting Earth's figure axis," NASA officials said.

Gross said his findings are based on early data available on the Chile earthquake. As more information about its characteristics are revealed, his prediction of its effects will likely change.

The Chile earthquake has killed more than 700 people and caused widespread devastation in the South American country.

Several major telescopes in Chile's Atacama Desert have escaped damage, according to the European Southern Observatory managing them.

A salt-measuring NASA satellite instrument destined to be installed on an Argentinean satellite was also undamaged in the earthquake, JPL officials said.

The Aquarius instrument was in the city of Bariloche, Argentina, where it is being installed in the Satelite de Aplicaciones Cientificas (SAC-D) satellite. The satellite integration facility is about 365 miles (588 km) from the Chile quake's epicenter.

The Aquarius instrument is designed to provide monthly global maps of the ocean's salt concentration in order to track current circulation and its role in climate change.

Chile Earthquake May Have Shortened Days on Earth - Yahoo! News

Not sure how much practical effect this has, but interesting nonetheless.

**troung** · 03 Mar 10,, 00:09

How many of our valueless non-Gold backed dollars do they need to pretend to research this....

**Parihaka** · 03 Mar 10,, 00:15

One Earth day is about 24 hours long. Over the course of a year, the length of a day normally changes gradually by one millisecond. It increases in the winter, when the Earth rotates more slowly, and decreases in the summer, Gross has said in the past.

Pardon?

**gunnut** · 03 Mar 10,, 00:15

Originally Posted by troung

How many of our valueless non-Gold backed dollars do they need to pretend to research this....

It was part of the "porkulus" package that may have saved or created these jobs?

**gunnut** · 03 Mar 10,, 00:16

Originally Posted by Parihaka

Pardon?

I read that part. I didn't know what it meant so I didn't want to question a "scientist."

)

**highsea** · 03 Mar 10,, 00:46

Yeah, hell. We speed up, slow down, wobble around...

It's really kind of a sloppy way to run a planet, when you come right down to it.

**Officer of Engineers** · 03 Mar 10,, 04:33

Originally Posted by Parihaka

Pardon?

And this freak is a scientist? When it's summer in the northern hemisphere, it's winter in the southern hemisphere and vice versa. In other words, it might speed in the north but it sure slows down in the south ... and vice versa.

BUT be that as it may, THERE WAS NOT EXTERNAL FORCE exerted by the Chilean earthquakes. By Newton's 3rd Law, for every action, there is an equal and opposite reaction, the earth slowing down would violate that law.

**guicho80** · 03 Mar 10,, 05:12

Unless i am mistaken, there is no violation of Newtons 3rd law there. A spinning figure skater can lessen or increase their angular velocity by shifting their mass towards or away from their axis of rotation, e.g. extending their arms or drawing them close to their body. Im guessing this chile quake shifted around enough of the earths crust to affect its rotational period.

**Officer of Engineers** · 03 Mar 10,, 05:14

By extending both arms. Only one arm in this case is extended.

**guicho80** · 03 Mar 10,, 05:25

One arm is sufficient no? Any amount matter being moved closer or farther from the axis of rotation should effect the angular velocity. Of course if you are a figure skater you are going to want to go with both arms and maybe a leg to make the effect more dramatic.

**Officer of Engineers** · 03 Mar 10,, 05:38

You're not seeing it. Chile is only one spot on the earth. The opposite end has to slow down. Chile may go faster but her opposite in the Aussie side will slow down.

**guicho80** · 03 Mar 10,, 05:48

I see what you are saying. But i dont believe that angular momentum works that way. It is not necessary for anything on the other side of the globe to shift in order for a change to occur. If a big chunk of Chile settles a few meters closer to the axis of rotation, it will change the earth's moment of inertia regardless of whats going on on the opposite side of the globe.

**Officer of Engineers** · 03 Mar 10,, 05:49

It has to ... or the Earth falls apart.

**RustyBattleship** · 03 Mar 10,, 06:05

Seismographic stations throughout the entire world recorded the Earthquake. Latest analysis is that the entire planet DID get a "jolt".

Who knows? Maybe we can do away with Leap Year.

**highsea** · 03 Mar 10,, 18:59

Rotation does fluctuate, and over time it has slowed due to the moon and earth getting further apart.

There are other factors that cause short term fluctuations, interactions between the core and mantle, wind and tides, ENSO, etc.

The rotation data shows oscillations over several different timescales. The one with the largest variation is seasonal: Earth slows down in January and February.

"It turns out that during the Northern Hemisphere winter, the winds - which are predominantly west to east - are stronger," Salstein said.

The more forceful winds double the angular momentum of the atmosphere. Angular momentum is a conserved quantity in nature - the example usually given is the spinning ice skater conserving angular momentum by speeding up when she brings her arms in.

In this case, the whole system - comprised of the spinning Earth and swirling atmosphere - adjusts to the blustery winter months by slowing down the solid Earth's rotation. This means the days get longer - by a few thousandths of a second.

The winter in the Southern Hemisphere does not produce the same increase in wind because the bottom of the world is mostly ocean and the temperature swings are, therefore, not as great.

A New Spin on Earth's Rotation | LiveScience