Asian earthquake and tsunami moved islands, shortened days

Asian earthquake and tsunami moved islands, shortened days

Jim Loney, Reuters/Jakarta

The massive earthquake that triggered the Asian tsunami wobbled
the earth on its axis, forced cartographers back to the drawing
board and changed time by a fraction, but there's no need to
adjust your clocks.

Six weeks after the tsunami that may have killed 300,000
people on the shores of the Indian Ocean, scientists are
discovering more about the changes wrought by the magnitude-9
quake, the fourth-largest in the last century.

It caused upheaval on the sea floor near its epicenter off the
northwest coast of Indonesia's Sumatra island and moved several
other islands, but scientists say any movement of land mass can
be measured in inches rather than tens of yards.

Chen Ji, a seismologist at the California Institute of
Technology, said he found movement along the fault line of about
33 feet laterally and 13-16 feet vertically.

But reports that the entire island of Sumatra -- 1,060 miles
long and 250 miles wide -- moved 115 feet or more are wildly
inaccurate, scientists say.

"We know we have movements of over a meter, perhaps a couple
of meters," said Ken Hudnut, a California-based geophysicist with
the U.S. Geological Survey. "But the idea that Sumatra has moved
100 feet is just wrong."

Scientists are working on precise measurements by comparing
geographic points whose locations were known before the quake
with their new positions using the Global Positioning System,
which reads exact locations by satellite.

High-tech British and U.S. ships are investigating changes to
the sea bed and local authorities are measuring depths in
critical shipping channels.

Shorter day
Scientists at NASA, the U.S. space agency, said the Dec. 26 quake
-- the largest to rattle Earth since 1964 in Alaska -- disrupted
the planet's rotation and shaved 2.68 microseconds, or millionths
of a second, from the length of a day.

NASA scientists B. F. Chao and Richard Gross calculated it
shifted Earth's mean north pole about 1 inch and made the planet
slightly less oblate, or flattened at the poles.

Physically, this is analogous to a spinning skater drawing
arms closer to the body, resulting in a faster spin," they wrote
in an article in Eos, a publication of the American Geophysical
Union.

But they said these changes are based on calculations rather
than measurements. The changes are so small they are either
difficult to measure or too small to detect.

Many earthquakes shake the planet's axis and affect its
rotation, scientists added, but their impact is too small to
measure.

But environmental damage from the tsunami was vast. The killer
waves gouged beaches, crushed coral reefs, smashed thousands of
acres of mangrove forests and refashioned coastlines from
Thailand to Somalia.

A preliminary survey by Indonesia's government and the United
Nations Environmental Program (UNEP) estimated the economic cost
to the environment at $675 million in Indonesia alone.

The survey said 60,000 acres of mangroves and 70,000 acres of
coral reefs were damaged.

Reefs, mangroves

Some coral reefs -- undersea gardens that act as shelter and
nursery to a wide range of marine species -- were crushed by the
waves. Corals grow slowly, some only an inch or two a year, so
their recovery could take decades.

John Pernetta, a UNEP official in Bangkok, said the extent of
damage to some of the coral reefs around Thailand was very high
-- up to 80 percent in some places. Their recovery was uncertain.

Mangroves torn out by the waves will fare better, he said, as
they leave behind roots and seeds that will help them regenerate.

"Long-term damage to mangroves by hurricanes or tsunamis
doesn't really happen," Pernetta said. "After five to 10 years
you don't even know anything has happened."

Vast stretches of Sumatra's west coast were turned brown by
the tsunami as rice paddies and other vegetation were swamped by
salt water. It could take two or three rainy seasons to wash the
salt from the saturated land, experts say.

The tsunami waves ate away beaches and coastal areas in
Thailand, Indonesia and Sri Lanka, radically changing maps.
The waves also carried sediment ashore, said Phil Liu, a Cornell
University wave researcher who led a scientific team to Sri Lanka
in mid-January.

"There is evidence that a lot of sediment was being brought
onshore," he said. "A post office on the east coast was found
with sediment deposits on the roof."

But it remains to be seen whether such sediment is good for
the land or a bane because of its high salt content.