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The maps below show the *permanent* displacement of the Earth's surface as measured by GPS stations in Japan, courtesy of our colleagues at the Geodetic Observation Center in the Geospatial Information Authority of Japan (analogous to our role as the Nevada Geodetic Laboratory in the Nevada Bureau of Mines and Geology).
|Horizontal Motion||Vertical Motion|
Click image for larger view. Note the scale of "50cm" on left figure and "10cm" on right figure, in the bottom right hand corners.
Images from GEONET, Geodetic Observation Center, Geospatial Information Authority of Japan, courtesy of Hiromitchi Tsuji, Head of the Satellite Geodesy Division.
Japan's coastline has moved up to 5 meters (>16 feet), and the location of the North Pole has been estimated to have moved about 10 cm (4 inches). The earthquake took place under the North American plate, which extends to Japan north of the Pacific plate via Alaska and Kamchatka. Here, the Pacific plate moves westward about 83 mm/yr, diving beneath North America off the east coast of Japan (star in figure indicates location of epicenter).
Here the colliding plates were tightly locked together like a giant spring below the seafloor until Friday March 11. With all the built up strain, the locked plates snapped in the magnitude 9.0 earthquake. Within about 3 minutes, the Pacific plate thrust down under North America, releasing the built up strain, causing the coastline of Japan (North America) to rebound eastward about 16 feet.
The Nevada Bureau of Mines and Geology has a 300-station GPS network in Nevada and eastern California. If a large earthquake were to happen here, we would produce a map similar to the one in Japan, and interpret what happened.
Right now we can clearly see strain building up across western Nevada. These measurements are essential for assessing earthquake hazards in Nevada. Such research along with NBMG's outreach on earthquake preparedness is clearly important to Nevada citizens.
More information on the Sendai Earthquake is being gathered at these sites: