Earthquake Affected The Earth’s Rotation

According to scientific findings, the earthquake on Friday in Japan affected the earth in a “slight” way.  Here are some quotes:



LOS ANGELES — The earthquake that struck Friday off the coast of Japan was so strong it moved the island of Honshu 8 feet to the east and sped up the Earth’s rotation by 1.6 microseconds, making the day just a little shorter, scientists said. A microsecond is one-millionth of a second.

A preliminary study by the Italian Institute of Geology and Volcanology indicate the quake may have shifted the Earth’s rotation axis by 3.937 inches, said Antonio Piersanti, researcher of the Rome-based institute, in an e-mailed statement Friday.

Earthquakes can involve shifting rock by several meters, changing the distribution of mass on the planet. This affects the Earth’s rotation, said Richard Gross, a geophysicist at the National Aeronautics and Space Administration.


Although imperceptible to humans, days will be a tiny bit shorter after Friday’s magnitude 8.9 earthquake off the coast of Japan.

NASA geophysicist Richard Gross calculated that the Earth’s rotation accelerated by 1.6 microseconds because of the shift in mass caused by the massive quake — the fifth strongest since 1900.

That change in rotation speed is slightly more than the one caused by last year’s earthquake in Chile.   However, an even larger earthquake in Sumatra in 2004 caused a 6.8-microsecond shortening of the day, the Associated Press reported.

The quake was 700 times more powerful than the one that struck Haiti last year, but the death toll appears to be far lower than the 220,000-plus killed in the Caribbean.

Friday’s quake caused a rupture 186 miles long and 93 miles wide in the sea floor 80 miles off the eastern coast of Japan. It happened 15 miles beneath the sea floor.

“The energy radiated by this quake is nearly equal to one month’s worth of energy consumption” in the United States, said U.S. Geological Survey scientist Brian Atwater.

Two days earlier, the region was rattled by a 7.2 quake. Scientists now consider that a foreshock. Foreshocks are basically earthquakes and are identified as precursors only after another quake follows. After a foreshock, there is only a 5 percent chance of an even bigger quake coming later.

“This was one of the rare instances where a big earthquake is followed by a bigger earthquake,” said USGS geophysicist Doug Given.


As of Saturday morning, Universal Time, which is five hours ahead of Eastern Standard Time, the U.S. Geological Survey showed there had been 365 earthquakes of at least 4.5 magnitude in the last seven days. Scientists said the number is about average.

For those of you who want to know more about the Earth and its rotation:


But on a longer timescale, Earth’s rotation can change by as much as 4 milliseconds as it did at the beginning of the 20th century. During these longer time-scale variations in rotation the Earth’s global average surface air temperature also changes by up to 0.4 degree Fahrenheit – though no one really knows why.


Animation of the Earth’s Rotation

G. D. Williams       © 2011