Thursday, March 4, 2010

Chile Quake Shifted Earth's Axis, Shortened Day

NASA: Quake Shifted Earth's Axis, Shortened Day:

A part from claiming the lives of hundreds of people and wreaking enormous property damage, Chile's massive earthquake has likely altered the distribution of the Earth's overall mass, scientists from NASA say.

As a result, the length of a day is now a little shorter than it was before Saturday's magnitude 8.8 earthquake.

"The length of the day should have gotten shorter by 1.26 microseconds [millionths of a second]," Richard Gross, a geophysicist at NASA's Jet Propulsion Laboratory,. "The axis about which the Earth's mass is balanced should have moved by 2.7 milliarcseconds [about 8 centimeters or 3 inches]."

"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.

2010 Chile Earthquake Born in 1960?

The recent Earth-axis jolt may have been the result of stress buildup from a magnitude 9.5 quake that struck Chile in 1960, scientists announced in a separate study yesterday.

"The story is quite similar to the December 26, 2004, magnitude 9.0 Sumatra earthquake, which was followed by a magnitude 8.7 quake on [the Sumatra fault's] southern end on the 28th of March 2005," geologist Jian Lin of Woods Hole Oceanographic Institution in Massachusetts said in a statement.

"The only difference is that it took 50 years for the northern neighboring section of the 1960 [Chile] earthquake to rupture, while it took only three months for the southern adjacent segment to rupture in Sumatra."

It's unclear why the Chile fault took so much longer than the Sumatra fault to "follow up," Lin added.

"But even 50 years is short enough [to fall within] a person's lifetime," he said. "Thus, we should consider the earthquake-interaction possibility seriously."


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