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Q&A: Japanese earthquake and tsunami altered Earth rotation slightly

Quake altered Earth's rotation

According to various news sources, the Japanese earthquake and tsunami caused Earth to tilt/move 3 degrees off its axis. What is the end result of this tilt?

Let's start with this — the Japan earthquake and tsunami didn't change Earth's axis of rotation by 3 degrees. That would have had immediate and profound effects on life.

Dr. Richard Gross, a geophysicist at NASA's Jet Propulsion Laboratory, said his calculations show that "the position at which the figure axis intersects the surface of the Earth near the North Pole should have changed by about 6.5 inches." That equates to 0.00000139 degrees, Gross said.

Earth does wobble a little differently because the earthquake rearranged its mass slightly, Gross said, moving parts of Japan eastward by up to 13 feet. It also lowered a 250-mile coastal section of Japan by about 2 feet. That redistribution of Earth's mass quickened its rotation and shortened the day by 1.8 millionths of a second.

Scientists compare it to a skater who is spinning. As she moves her arms closer to her body, she spins faster. Similarly, as Earth's mass moves closer to its rotation axis, it spins quicker.

But it's nothing that anyone might notice.

"While earthquakes can change how the Earth rotates about its axis," Gross said, "they cannot change how the Earth orbits about the sun. In particular, they cannot change the Earth's tilt in space. Only external forces like the gravitational attraction of the sun and moon or the impact of an asteroid can do that. Internal forces like earthquakes or winds or ocean currents cannot."

The 9.0 earthquake was the fifth strongest in the world in the past century. More than 15,000 are dead, with damages estimated at $300 billion.

Radiation effects can be severe

In 1945, two atomic bombs were dropped on Japan. Has there been any study of long-term effects of this huge amount of radiation that would predict whether there will be long-term health effects from the power plant disaster?

A study in the Journal of the American Medical Association in 2006 found that nearly 45 percent of 4,100 survivors alive in the early 2000s had some type of thyroid disease, including nodules, autoimmune disease, hypothyroidism and hyperthyroidism. Also, radiation sickness and cancer are other risks for people affected by radiation from any source, not just at the Fukushima Daiichi nuclear power plant, Malcolm Sperrin, a medical physicist, told the BBC.

Radiation sickness can damage internal organs, which can be fatal. But cancer is the biggest long-term risk, the BBC wrote. Also, "failure to properly repair the damage caused by radiation can also result in changes . . . to the body's genetic material, which are not only associated with cancer, but may also be potentially passed down to offspring, leading to deformities in future generations. These can include smaller head or brain size, poorly formed eyes, slow growth and severe learning difficulties."

Q&A: Japanese earthquake and tsunami altered Earth rotation slightly 06/23/11 [Last modified: Thursday, June 23, 2011 4:30am]
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