Sismo no Chile leva a dias mais curtos na Terra!

O terramoto no Chile levou a uma pequena mudança no eixo de rotação da Terra, e levou a que a Terra rode mais depressa, o que faz com que os dias passem a ser mais curtos!

Ambos os efeitos são PREVISÕES a partir de modelos de computador.
É que as mudanças são tão pequenas e irrisórias, que ninguém as consegue medir fisicamente.
Na prática, nada mudou 🙂

Por isso, escusam de se pôr histéricos e com mensagens de medo! 🙂
Nada de histerismos 🙂

Público:
“O sismo de 27 de Fevereiro no Chile que matou mais de 700 pessoas terá feito os dias na Terra mais curtos – embora imperceptivelmente, apenas 1,26 milionésimos de segundo mais curtos. Mas o eixo de rotação do planeta ter-se-á deslocado cerca de oito centímetros, em resultado do abalo de magnitude 8,8 na escala de Richter.
Estes cálculos são produto de um modelo informático usado pelo geofísico do Laboratório de Propulsão a Jacto da NASA Richard Gross. E não são algo inédito, que apenas tenha acontecido com este tremor de terra: estes efeitos acontecem quando se verificam grandes deslocações de massa no planeta.
Por exemplo, no terramoto de 9,1 na escala de Richter de Sumatra e no tsunami do Sudoeste Asiático que se lhe seguiu, a 26 de Dezembro de 2004, o dia terá diminuído 6,8 milionésimos de segundo e o eixo da Terra (a linha imaginária em torno do qual a Terra roda sobre si própria) ter-se-á deslocado sete centímetros.
Fala-se sempre no condicional porque é difícil verificar experimentalmente estas previsões feitas através de cálculos computadorizados. As mudanças são demasiado pequenas para serem detectadas em termos físicos.”
(…)

Ciência Hoje:
“Sismo no Chile terá reduzido duração de dias na Terra.”
(…)

Universe Today:
“One scientist says the shaking may have affected the entire planet by shifting Earth on its axis. This possibly may have shortened the length of each day on Earth by about 1.26 microseconds. Using a complex model JPL research scientist Richard Gross computed how Earth’s rotation should have changed as a result of the Feb. 27, 2010 quake. If his figures are correct, the quake should have moved Earth’s figure axis (the axis about which Earth’s mass is balanced) by 2.7 milliarcseconds (about 8 centimeters, or 3 inches).”
(…)

Space.com:
“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 microseconds, according to research scientist Richard Gross at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. One microsecond is one-millionth of a second long.
(…)
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).
“Perhaps more impressive is how much the quake shifted Earth’s axis,” NASA officials said in a Monday update.
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).
(…)
One Earth day is about 24 hours, or 86,400 seconds, long. Over the course of a year, the length of a day normally changes gradually by about one millisecond, which is 1,000 microseconds.
That variation is due to seasonal variations in the Earth’s ocean currents and the atmosphere’s jet stream, Gross said. As the jet stream shifts southward during the winter months in the Earth’s northern hemisphere, the length of the day gradually changes, he said.
In the past, Gross has said that Earth’s rotation slows down slightly in those winter months, then picks back up in the summer.
(…)
Gross said his findings are based on early data available on the Chile earthquake. He is confident in the computer model’s accuracy, with only slight tweaks expected to be required, he said.”

JPL:
“The Feb. 27 magnitude 8.8 earthquake in Chile may have shortened the length of each Earth day.
JPL research scientist Richard Gross computed how Earth’s rotation should have changed as a result of the Feb. 27 quake. Using a complex model, he and fellow scientists came up with a preliminary calculation that the quake should have shortened the length of an Earth day by about 1.26 microseconds (a microsecond is one millionth of a second).”
(…)

NASA:
“Perhaps more impressive is how much the quake shifted Earth’s axis. Gross calculates the quake should have moved Earth’s figure axis (the axis about which Earth’s mass is balanced) by 2.7 milliarcseconds (about 8 centimeters, or 3 inches). Earth’s figure axis is not the same as its north-south axis; they are offset by about 10 meters (about 33 feet).”
(…)

Abstract do modelo usado?
“The static displacement field generated by an earthquake has the effect of rearranging the Earth’s mass distribution and will consequently cause the Earth’s rotation and gravitational field to change. Although the coseismic effect of earthquakes on the Earth’s rotation and gravitational field have been modeled in the past, no unambiguous observations of this effect have yet been made.
However, the Gravity Recovery And Climate Experiment (GRACE) satellite, which is scheduled to be launched in 2001, will measure time variations of the Earth’s gravitational field to high degree and order with unprecedented accuracy.
In this presentation, the modeled coseismic effect of earthquakes upon the Earth’s gravitational field to degree and order 100 will be computed and compared to the expected accuracy of the GRACE measurements. In addition, the modeled second degree changes, corresponding to changes in the Earth’s rotation, will be compared to length-of-day and polar motion excitation observations.”