Chile earthquake may shorten days

The massive 8.8 earthquake that struck Chile may have changed the entire Earth's rotation and shortened the length of days on our planet, a NASA scientist said Monday.

The quake, the seventh strongest earthquake in recorded history, hit Chile Saturday and should have shortened the length of an Earth day by 1.26 milliseconds, according to research scientist Richard Gross at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

 "Perhaps more impressive is how much the quake shifted Earth's axis," NASA officials said in a Monday update.

 The computer model used by Gross and his colleagues to determine the effects of the Chile earthquake effect also found that it should have moved Earth's figure axis by about 3 inches (8 cm or 27 milliarcseconds).  

 The Earth's figure axis is not the same as its north-south axis, which it spins around once every day at a speed of about 1,000 mph (1,604 kph).

 The figure axis is the axis around which the Earth's mass is balanced. It is offset from the Earth's north-south axis by about 33 feet (10 meters).

 Strong earthquakes have altered Earth's days and its axis in the past. The 9.1 Sumatran earthquake in 2004, which set off a deadly tsunami, should have shortened Earth's days by 6.8 microseconds and shifted its axis by about 2.76 inches (7 cm, or 2.32 milliarcseconds).

 One Earth day is about 24 hours long. Over the course of a year, the length of a day normally changes gradually by one millisecond. It increases in the winter, when the Earth rotates more slowly, and decreases in the summer, Gross has said in the past.

 The Chile earthquake was much smaller than the Sumatran temblor, but its effects on the Earth are larger because of its location. Its epicenter was located in the Earth's mid-latitudes rather than near the equator like the Sumatran event.

 The fault responsible for the 2010 Chile quake also slices through Earth at a steeper angle than the Sumatran quake's fault, NASA scientists said.

 "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.

 Gross said his findings are based on early data available on the Chile earthquake. As more information about its characteristics are revealed, his prediction of its effects will likely change