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Chile earthquake may have shortened days
Seventh strongest quake in recorded history may have shifted Earth's axis
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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.
The Chile earthquake has killed more than 700 people and caused widespread devastation in the South American country.
Several major telescopes in Chile's Atacama Desert have escaped damage, according to the European Southern Observatory managing them.
A
salt-measuring NASA satellite instrument destined to be installed on an
Argentinean satellite was also undamaged in the earthquake, JPL
officials said.
The
Aquarius instrument was in the city of Bariloche, Argentina, where it
is being installed in the Satelite de Aplicaciones Cientificas (SAC-D)
satellite. The satellite integration facility is about 365 miles (588
km) from the Chile quake's epicenter.
The
Aquarius instrument is designed to provide monthly global maps of the
ocean's salt concentration in order to track current circulation and
its role in climate change.