- MELBOURNE (Reuters) -- Two
weeks on, the earth is still vibrating from the massive undersea earthquake
off Indonesia that triggered the tsunami, Australian researchers said on
Sunday.
-
- The Australian National University (ANU) said the reverberations
were similar in form to the ringing of a bell, though without the sound,
and were picked up by gravity monitoring instruments.
-
- "These are not things that are going to throw you
off your chair, but they are things that the kinds of instruments that
are in place around the world can now routinely measure," said ANU
Earth Sciences researcher Herb McQueen.
-
- "It is certainly above the background level of vibrations
that the earth is normally accustomed to experiencing." The magnitude
9.0 earthquake, the strongest for 40 years, struck off the coast of Indonesia's
Sumatra island on December 26. The tsunami it generated claimed more than
156,000 lives.
-
- Mr McQueen said the oscillation was fading and at current
levels equated to about a millimetre of vertical motion of the earth.
-
- Immediately after the quake the oscillation was probably
in the 20 to 30 cm motion range that is typically generated in the earth
by the movements of the sun and moon. "This particular earthquake
because it was 10 times larger than most of the recent large earthquakes
is continuing to reverberate," Mr McQueen said.
-
- "We can still see a steady signal of the earth vibrating
as a result of that earthquake two weeks later. From what it looks like,
it appears it will probably continue to oscillate for several more weeks."
-
- The ANU's gravity meter is housed in a fireproof basement
at the Mount Stromlo Observatory near the capital Canberra and is part
of a global geodynamics project established after major earthquakes in
the 1960s.
-
- US scientists said just after the quake that it may have
permanently accelerated the Earth's rotation -- shortening days by a fraction
of a second -- and caused the planet to wobble on its axis.
-
- Richard Gross, a geophysicist with Nasa's Jet Propulsion
Laboratory in California, theorised that a shift of mass towards the earth's
centre during the quake caused the planet to spin three millionths of a
second faster and tilt about 2.5 cm on its axis.
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reserved.
-
- http://economictimes.indiatimes.com/articleshow/985440.cms
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