Chile Earthquake May Have Shortened Days on Earth

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.

“This change should be permanent,” Gross told SPACE.com today. There is a chance the Earth’s rotation could relax over time, but it is too early to tell, he said.

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).

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, 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.

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

Gross compared the Sumatran event to a figure skater drawing her arms inward during a spin to turn faster on the ice. Since the Sumatran quake was closer to the Earth’s equator, its day-shortening effect is stronger than the Chile temblor, he said.

But 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. He is confident in the computer model’s accuracy, with only slight tweaks expected to be required, he said.

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

1. Earth has been more seismologically active in the past 15 years or so, says Stephen S. Gao, a geophysicist at Missouri University of Science & Technology. Not all seismologist agree, however.

2. San Francisco is moving toward Los Angeles at the rate of about 2 inches per year — the same pace as the growth of your fingernails — as the two sides of the San Andreas fault slip past one another. The cities will meet in several million years. However, this north-south movement also means that despite fears, California won't fall into the sea.

3. March is not earthquake month, despite what some people believe. True, on March 28, 1964, Prince William Sound, Alaska, experienced a 9.2 magnitude event — one of the biggest ever. It killed 125 people and caused $311 million in property damages. And on March 9, 1957, the Andreanof Islands, Alaska, felt a 9.1 temblor. But the next three biggest U.S. earthquakes occurred in February, November, and December. The devastating major earthquake in Chile of 2010 struck on Feb. 27. And the huge 9.3 temblor that spawned the devastating Indian Ocean tsunami in 2004 occurred on Dec. 26.

4. There are about 500,000 earthquakes a year around the world, as detected by sensitive instruments. About 100,000 of those can be felt, and 100 or so cause damage each year. Each year the southern California area alone experiences about 10,000 earthquakes, most of them not felt by people.

5. The sun and moon cause tremors. It's long been known that they create tides in the planet's crust, very minor versions of ocean tides. Now researchers say the tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground.

6. A city in Chile moved 10 feet in the massive 8.8 magnitude earthquake Feb. 27, 2010. The rip in Earth's crust shifted the city of Concepción that much to the west. The quake is also thought to have changed the planet's rotation slightly and shortened Earth's day.

7. There's no such thing as "earthquake weather." Statistically, there is an equal distribution of earthquakes in cold weather, hot weather, rainy weather, and so on, according to the U.S. Geological Survey. Scientists say there is no physical way that weather could affect the forces several miles beneath the surface of the earth where quakes originate. The changes in barometric pressure in the atmosphere are very small compared to the forces in the crust, and the effect of the barometric pressure does not reach beneath the soil.

8. Earth's bulge was trimmed a little by the 2004 Indonesian earthquake, the 9.0+ temblor that generated the deadly tsunami on Dec. 26 that year. Earth's midsection bulges in relation to the measurement from pole-to-pole, and the catastrophic land displacement caused a small reduction in the bulge, making the planet more round.

9. The Pacific Ring of Fire is the most geologically active region of Earth. It circles the Pacific Ocean, touching the coasts North and South America, Japan, China and Russia. It's where the majority of Earth's major quakes occur as major plate boundaries collide.

10. Oil extraction can cause minor earthquakes. These are not the quakes you read about. Rather, because oil generally is found in soft and squishy sediment, when oil is removed other rock moves in to fill the void, creating "mini-seismic events" that are not noticeable to humans.

11. The largest earthquake ever recorded was a magnitude 9.5 in Chile on May 22, 1960.

12. Quakes on one side of Earth can shake the other side. Seismologists studying the massive 2004 earthquake that triggered killer tsunamis throughout the Indian Ocean found that the quake had weakened at least a portion of California's famed San Andreas Fault. The Chilean quake of 1960 shook the entire Earth for many days, a phenomenon called oscillation that was measured by seismic stations around the planet.

13. The deadliest earthquake ever struck January 23, 1556 in Shansi, China. Some 830,000 are estimated to have died.