Google News (Link) - AFP (March 12, 2011)
Japan�s recent massive earthquake, one of the largest ever recorded, appears to have moved the island by about eight feet (2.4 meters), the US Geological Survey said.
�That�s a reasonable number,� USGS seismologist Paul Earle told AFP. �Eight feet, that�s certainly going to be in the ballpark.�
Friday�s 8.9 magnitude quake unleashed a terrifying tsunami that engulfed towns and cities on Japan�s northeastern coast, destroying everything in its path in what Prime Minister Naoto Kan said was an �unprecedented national disaster.�
The quake and its tectonic shift resulted from �thrust faulting� along the boundary of the Pacific and North America plates, according to the USGS.
The Pacific plate pushes under a far western wedge of the North America plate at the rate of about 3.3 inches (83 millimeters) per year, but a colossal earthquake can provide enough of a jolt to dramatically move the plates, with catastrophic consequences.
�With an earthquake this large, you can get these huge ground shifts,� Earle said. �On the actual fault you can get 20 meters (65 feet) of relative movement, on the two sides of the fault.�
He said similar movements would have been seen for Chile and Indonesia.
In December 2004, a 9.1 magnitude quake off Sumatra caused a tsunami that killed an estimated 228,000 people. An 8.8 quake off the coast of Chile in February 2010 killed more than 500.
There was not a similar ground shift in the 7.0 earthquake that devastated Haiti in February 2010, Earle said.
�A magnitude 7.0 is much smaller than the earthquake that just happened in Japan,� he said. �We�ve had aftershocks (in Japan) larger than the Haiti earthquake.�
Kenneth Hudnut, a USGS geophysicist, said experts read data including from global positioning systems to determine the extend of the shift.
�We know that one GPS station moved (eight 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,� he told CNN. �