Around mid 1978 a scientific magazine had an item on the shift of axis
of the earth due to earthquakes. Sorry but searching has not found the
item. My, not to be relied on memory, thinks that it was from the
French Bureau International de l'Heure in Science or Scientific American
Cheers,
Will
On 07/27/2016 10:45 AM, Tom Van Baak wrote:
Hal Murray wrote:
I've seen mention that the rotation rate of the Earth changed by a few
microseconds per day as a result of the 2011 earthquake in Japan. Does that
show up in any data? Your recent graph doesn't go back that far and it's got
a full scale of 2000 microseconds so a few is going to be hard to see.
Right. The IERS graphs I posted are real measurements of earth rotation. The
earthquake / tsunami numbers are theoretical calculations only; numbers far
smaller than what can be measured.
A couple of guys at NASA have carefully modeled all of this and the predictions
are quite interesting. It's just that the official NASA/JPL press releases,
once filtered by the popular press, give the impression that these are
worrisome or real measurable effects on the earth's rotation rate or axis tilt.
Instead they are order(s) of magnitude below what can be measured, given the
level of VLBI resolution or earth rotation noise.
Here are three recent press releases:
2005 "NASA Details Earthquake Effects on the Earth"
http://www.jpl.nasa.gov/news/news.php?feature=716
2010 "Chilean Quake May Have Shortened Earth Days"
http://www.nasa.gov/topics/earth/features/earth-20100301.html
2011 "Japan Quake May Have Shortened Earth Days, Moved Axis"
http://www.nasa.gov/topics/earth/features/japanquake/earth20110314.html
Google for Richard Gross and Benjamin Fong Chao for more information.
/tvb
----- Original Message -----
From: "Hal Murray" <hmur...@megapathdsl.net>
To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and frequency
measurement" <time-nuts@febo.com>
Cc: <hmur...@megapathdsl.net>
Sent: Saturday, July 23, 2016 5:59 PM
Subject: Q/noise of Earth as an oscillator
t...@leapsecond.com said:
Earth is a very noisy, wandering, drifting, incredibly-expensive-to-measure,
low-precision (though high-Q) clock.
What is the Q of the Earth? It might be on one of your web pages, but I
don't remember seeing it. Google found a few mentions, but I didn't find a
number.
I did find an interesting list of damping mechanisms in a geology book.
Geology-nuts are as nutty as time-nuts. Many were discussing damping of
seismic waves rather than rotation.
I've seen mention that the rotation rate of the Earth changed by a few
microseconds per day as a result of the 2011 earthquake in Japan. Does that
show up in any data? Your recent graph doesn't go back that far and it's got
a full scale of 2000 microseconds so a few is going to be hard to see.
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