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Posted

I was reading an old article in Time mag about the earthquake in Chile that that made the day shorter. Nasa says it's shorter by 1.26th millionths of a second earlier because of the subterranean upheaval.

 

Can some one please explain when earthquakes occur, how do they add or take away from the official clock in the US? Do they change it right after the event or wait until the new year comes around or just whenever they get around to it?

 

Because earthquakes alter planetary speeds by shifting plates and rearranging the Earths mass how can time keepers evaluate the different bulges in the Earth and reconfigure these changes to calculate the new time? thx

 

Deepwater

Posted

I was reading an old article in Time mag about the earthquake in Chile that that made the day shorter. Nasa says it's shorter by 1.26th millionths of a second earlier because of the subterranean upheaval.

 

Can some one please explain when earthquakes occur, how do they add or take away from the official clock in the US? Do they change it right after the event or wait until the new year comes around or just whenever they get around to it?

 

Because earthquakes alter planetary speeds by shifting plates and rearranging the Earths mass how can time keepers evaluate the different bulges in the Earth and reconfigure these changes to calculate the new time? thx

 

...

 

Also forgot one more question, at what height is the official clock kept.

 

the clocks are not reset for earthquakes as i read it. since the day was shorter, the rotation rate sped up which would require a negative leap second & while possible, this article says none have ever been used.

 

The International Earth Rotation and Reference Systems Service (IERS) announces the insertion of a leap second whenever the difference between UTC and UT1 approaches 0.6 s, to keep the difference between UTC and UT1 from exceeding 0.9 s. IERS publishes announcements every six months, whether leap seconds are to occur or not, in its "Bulletin C". Such announcements are typically published well in advance of each possible leap second date — usually in early January for June 30 and in early July for December 31. Because the Earth's rotation rate is unpredictable in the long term, it is not possible to predict the need for them more than six months in advance.

 

The most recent leap second was added at the end of December 31, 2008.[10][11]

 

After 23:59:59 UTC, a positive leap second at 23:59:60 would be counted, before the clock indicates 00:00:00 of the next day. Negative leap seconds are also possible, should the Earth's rotation become slightly faster — in which case, 23:59:58 would be followed directly by 00:00:00 — but they have not yet been used. Leap seconds occur only at the end of a UTC month, and have only ever been inserted at the end of June 30 or December 31. Unlike leap days, they occur simultaneously worldwide; for example, the leap second on December 31, 2005 occurred at 23:59:60 UTC. This was 18:59:60 (6:59:60 p.m.) U.S. Eastern Standard Time and 08:59:60 (8:59:60 a.m.) on January 1, 2006 Japan Standard Time.

 

 

Historically, leap seconds have been inserted about every 18 months. From June 1972 through December 2008, the BIH/IERS gave instructions to insert a leap second on 24 occasions, after an initial 10 second offset from TAI on January 1, 1972. The seven-year interval between January 1, 1999 and December 31, 2005 was the longest period without a leap second since the system was introduced.

 

Some time signal broadcasts give voice announcements of an impending leap second.

http://en.wikipedia.org/wiki/Leap_second

 

 

according to the united states naval observatory,

...The DoD common time reference is the U.S. Naval Observatory Master Clock. It is generated at USNO in Washington, D.C. and at the Alternate Master Clock Facility at Schriever AFB in Colorado.

http://www.usno.navy.mil/USNO/time

 

moreover, it isn't just one clock at those facilities.

Clocks Currently in the USNO Time Scale

Currently, the USNO Washington, DC mean time scale includes

44 atomic clocks:

13 hydrogen masers

 

31 cesiums

http://tycho.usno.navy.mil/

 

altitude @washington d.c

A USGC topo map shows Mount St. Alban in DC, on which the Washington cathedral sits, is regarded as the highest point in DC. At that point, the elevation is 377 feet.

Read more: http://wiki.answers.com/Q/What_is_the_altitude_of_Washington_DC#ixzz1WYpF1hoh

 

altitude @shriever afb

Peterson Air Force Base is located at an altitude of 6,035 feet on the east side of Colorado springs near the junction of highways US 24 and Colorado 94. The Base covers approximately 1,278 acres. Peterson Air Force Base is considered a joint-use installation because the airfield is owned and operated by the city of Colorado Springs, and collectively used by military and civilian aircraft. Other military installations in the area include:

 

Schriever Air Force Base

 

Fort Carson

 

United States Air Force Academy

...

 

http://www.cdphe.state.co.us/hm/peterson.htm

  • 6 months later...
Posted

http://abcnews.go.com/blogs/headlines/2012/03/mysterious-booms-and-trembles-plague-wisconsin-town-baffle-scientists/

 

I know there was another earthquake thread that Turtle was involved in, but I could not find it so I attached to this one. A similar thing happend once in Philadelphia last year, and they never figured out what it was.

 

woah! curiouser & curiouser. :reallyconfused: sounds like they need to set up some accoustic recording equipment in the immediate area to see if they can get a handle on the frequency(s), amplitude(s), and rate of occurance of the booms. :ebomb: :phones:

 

ps here's that other thread for future reference. (linked to last post) Earthquakes

  • 4 weeks later...
Posted

 

no. quoting your article:

...I emailed our good friend Matt Deutch, an engineer with the WWV atomic clock station, and asked if the Chilean earthquake meant that they needed a leap second on the atomic clock. Essentially, the change in the earth’s rotation this time did not amount to a full second, so no adjustments are required now. However, the next time a full second of rotational change is accumulated, this jolt will be part of that accumulation. ...

 

so while the article answers deepwater's question,:

Can some one please explain when earthquakes occur, how do they add or take away from the official clock in the US? Do they change it right after the event or wait until the new year comes around or just whenever they get around to it?

...

Deepwater

your "A leap second..." does not answer the question. do you have a specific point you'd like to make, or are you just looking for ways to provoke me?
  • 2 weeks later...
  • 2 months later...

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