Quake Moved Japan Coast 8 Feet; Shifted Earth’s Axis; Shortened Days On Earth (Updated)

Quake Moved Japan Coast 8 Feet; Shifted Earth’s Axis; Shortened Days On Earth (Updated)

Mar 27

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This video shows the swarm of earthquakes that assaulted Japan between March 9 and March 14. Every second of the film marks an hour in real time. The big 9.0 earthquake of March 11th takes place around 1:17.

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http://www.youtube.com/watch?v=xOfy1CoxrMo

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QUAKE MOVED JAPAN COAST 8 FEET; SHIFTED EARTH’S AXIS
By Kevin Voigt
CNN
March 12, 2011

Original Link

The powerful earthquake that unleashed a devastating tsunami Friday appears to have moved the main island of Japan by 8 feet (2.4 meters) and shifted the Earth on its axis.

“At this point, we know that one GPS station moved (8 feet), and we have seen a map from GSI (Geospatial Information Authority) in Japan showing the pattern of shift over a large area is consistent with about that much shift of the land mass,” said Kenneth Hudnut, a geophysicist with the U.S. Geological Survey (USGS).

Reports from the National Institute of Geophysics and Volcanology in Italy estimated the 8.9-magnitude quake shifted the planet on its axis by nearly 4 inches (10 centimeters).

The temblor, which struck Friday afternoon near the east coast of Japan, killed hundreds of people, caused the formation of 30-foot walls of water that swept across rice fields, engulfed entire towns, dragged houses onto highways, and tossed cars and boats like toys. Some waves reached six miles (10 kilometers) inland in Miyagi Prefecture on Japan’s east coast.

The quake was the most powerful to hit the island nation in recorded history and the tsunami it unleashed traveled across the Pacific Ocean, triggering tsunami warnings and alerts for 50 countries and territories as far away as the western coasts of Canada, the U.S. and Chile. The quake triggered more than 160 aftershocks in the first 24 hours — 141 measuring 5.0-magnitude or more.

The quake occurred as the Earth’s crust ruptured along an area about 250 miles (400 kilometers) long by 100 miles (160 kilometers) wide, as tectonic plates slipped more than 18 meters, said Shengzao Chen, a USGS geophysicist.

Japan is located along the Pacific “ring of fire,” an area of high seismic and volcanic activity stretching from New Zealand in the South Pacific up through Japan, across to Alaska and down the west coasts of North and South America. The quake was “hundreds of times larger” than the 2010 quake that ravaged Haiti, said Jim Gaherty of the LaMont-Doherty Earth Observatory at Columbia University.

The Japanese quake was of similar strength to the 2004 earthquake in Indonesia that triggered a tsunami that killed over 200,000 people in more than a dozen countries around the Indian Ocean. “The tsunami that it sent out was roughly comparable in terms of size,” Gaherty said. “[The 2004 tsunami] happened to hit some regions that were not very prepared for tsunamis … we didn’t really have a very sophisticated tsunami warning system in the Indian Ocean basin at the time so the damage was significantly worse.”

The Japanese quake comes just weeks after a 6.3-magnitude earthquake struck Christchurch on February 22, toppling historic buildings and killing more than 150 people. The timeframe of the two quakes have raised questions whether the two incidents are related, but experts say the distance between the two incidents makes that unlikely.

“I would think the connection is very slim,” said Prof. Stephan Grilli, ocean engineering professor at the University of Rhode Island.

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HOW THE JAPAN EARTHQUAKE SHORTENED DAYS ON EARTH
Space.com
March 13, 2011

Original Link

The massive earthquake that struck northeast Japan Friday (March 11) has shortened the length Earth’s day by a fraction and shifted how the planet’s mass is distributed.

A new analysis of the 8.9-magnitude earthquake in Japan has found that the intense temblor has accelerated Earth’s spin, shortening the length of the 24-hour day by 1.8 microseconds, according to geophysicist Richard Gross at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Gross refined his estimates of the Japan quake’s impact – which previously suggested a 1.6-microsecond shortening of the day – based on new data on how much the fault that triggered the earthquake slipped to redistribute the planet’s mass. A microsecond is a millionth of a second.

“By changing the distribution of the Earth’s mass, the Japanese earthquake should have caused the Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds,” Gross told SPACE.com in an e-mail. More refinements are possible as new information on the earthquake comes to light, he added.

The scenario is similar to that of a figure skater drawing her arms inward during a spin to turn faster on the ice. The closer the mass shift during an earthquake is to the equator, the more it will speed up the spinning Earth.

One Earth day is about 24 hours, or 86,400 seconds, long. Over the course of a year, its length varies by about one millisecond, or 1,000 microseconds, due to seasonal variations in the planet’s mass distribution such as the seasonal shift of the jet stream.

The initial data suggests Friday’s earthquake moved Japan’s main island about 8 feet, according to Kenneth Hudnut of the U.S. Geological Survey. The earthquake also shifted Earth’s figure axis by about 6 1/2 inches (17 centimeters), Gross added.

The Earth’s figure axis is not the same as its north-south axis in space, 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 and the north-south axis by about 33 feet (10 meters).

“This shift in the position of the figure axis will cause the Earth to wobble a bit differently as it rotates, but will not cause a shift of the Earth’s axis in space — only external forces like the gravitational attraction of the sun, moon, and planets can do that,” Gross said.

This isn’t the first time a massive earthquake has changed the length of Earth’s day. Major temblors have shortened day length in the past.

The 8.8-magnitude earthquake in Chile last year also sped up the planet’s rotation and shortened the day by 1.26 microseconds. The 9.1 Sumatra earthquake in 2004 shortened the day by 6.8 microseconds.

And the impact from Japan’s 8.9-magnitude temblor may not be completely over.The weaker aftershocks may contribute tiny changes to day length as well.

The March 11 quake was the largest ever recorded in Japan and is the world’s fifth largest earthquake to strike since 1900, according to the USGS. It struck offshore about 231 miles (373 kilometers) northeast of Tokyo and 80 miles (130 km) east of the city of Sendai, and created a massive tsunami that has devastated Japan’s northeastern coastal areas. At least 20 aftershocks registering a 6.0 magnitude or higher have followed the main temblor.

“In theory, anything that redistributes the Earth’s mass will change the Earth’s rotation,” Gross said. “So in principle the smaller aftershocks will also have an effect on the Earth’s rotation. But since the aftershocks are smaller their effect will also be smaller.”

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EARTHQUAKE IS BIGGEST IN JAPAN’S RECORDED HISTORY
By Alexandra Witze
Wired
March 11, 2011

Original Link

The magnitude 8.9 quake that struck off Japan’s coast on March 11 will go down as one of the country’s largest earthquakes.

Even if its magnitude is downgraded in the coming days, as sometimes happens as more data are analyzed, the quake will remain a benchmark in a country that has seen many major quakes. It ranks fifth on the list of biggest quakes this past century. The Indonesian earthquake that spawned 2004’s devastating Indian Ocean tsunami was a magnitude 9.1.

Japan’s monster earthquake struck at 2:46 p.m. local time, about 150 km off the coast of the island of Honshu. Japan is one of the world’s most prepared societies when it comes to earthquakes, and a recently established early warning system broadcast alerts in many areas, including Tokyo, before the shaking began.

Seismic activity in the region began with a magnitude 7.2 quake on March 3. Major aftershocks continue to rattle the area. The death toll is unknown.

Japan owes its lively seismic existence to its precarious geologic setting. The islands of Japan formed where one great plate of Earth’s crust, the Pacific plate, dived beneath the Eurasian and Philippine plates. The collision is part of the “Ring of Fire” of earthquake and volcanic activity around the Pacific Ocean.

Chikyu, a deep-sea drilling vessel operated by the Japan Agency for Marine-Earth Science and Technology, is in the midst of a many-years study drilling into the seafloor off Japan’s coast to study the genesis of big quakes there.

The deadliest quake in Japan’s history came in 1923, when more than 140,000 people perished in the magnitude 7.9 Great Kanto Earthquake. That tremor was centered southwest of Tokyo Bay. The March 11 quake struck more to the north, offshore from the city of Sendai.

“Fortunately for Tokyo it’s a bit further north than the great Kanto earthquake was, which means the damage in Tokyo is likely to be much less,” Kevin McCue, a Canberra-based seismologist at CQUniversity in Australia, said in a statement.

Tsunami warnings spread across the Pacific in the hours after the earthquake; earthquakes generate tsunamis when the ground rupture displaces massive amounts of water. The size of the Japanese quake, plus its relatively shallow depth of 24 km, meant that it was primed to trigger tsunamis.

Honshu’s east coast had essentially no time to prepare for the waves, but other locations around the Pacific set into gear preparation and evacuation plans polished after the 2004 Indian Ocean tsunami. Hawaii was reporting waves of 1 meter or less.

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RELATED LINKS:

• Japanese 03/11/11 Earthquake-Tsunami & Aftermath Resource Page
BBC Videos of 03/11/11 Japan Earthquake
Boston Globe Photos of 03/11/11 Japan Earthquake
Daily Mail Photos of 03/11/11 Japan Earthquake
More Photos from The Daily Mail
Japan 03/11/11/ Earthquake: Before & After
Wikipedia on 2011 Sendai Earthquake & Tsunami
Google Crisis Response Page: 2011 Japanese Earthquake & Tsunami
Japanese 03/11/11 Earthquake-Tsunami Resource Page

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