Chilean Earthquake May Have Changed Length of a Day

By Bridget Tyler on March 3rd, 2010

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The massive 8.8 earthquake that hit Chile on in the wee hours of Saturday night didn’t just destroy buildings and wipe away seaside towns.  It quite probably changed the rotation of the Earth itself and shortened the length of days on our planet.

The quake was the seventh strongest earthquake in recorded history. According to NASA it should have shortened the length of a day by 1.26 milliseconds.  ”Perhaps more impressive is how much the quake shifted Earth’s axis,” NASA officials said in a Monday update.  The computer model NASA used to determine the effects of the earthquake on the planet also found that it should have moved Earth’s figure axis by about 3 inches.  Earth’s figure axis is the axis around which the Earth’s mass is balanced – the Earth rests at a 33 degree tilt from its north-south axis.

This isn’t the first time massive earthquakes have changed the way the Earth rotates on its axis.  The 9.1 earthquake in Sumatra in 2004 that set off that year’s record breaking, deadly tsunami, should have shortened Earth’s days by 6.8 microseconds and shifted its axis by about 2.76 inches.  The smaller Chilean earthquake caused a bigger shift because of its location – its epicenter was in Earth’s mid-latitudes, unlike the Sumatran event which was near the equator.  The fault that caused the Chile quake also cuts through the Earth at a steeper angle than the Sumatran fault, “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.