\n When massive 9.0 magnitude earthquake shook Japan on March 11, 2011, the ground also made a more lasting move. About 15 minutes after the event began at 2:46 p.m. local time, nearly the entire country shifted eastward, according to GPS station measurements.\n <\/p>\n
\n The lurch was small \u2014 5 to 6 millimeters, or 0.20 to 0.24 inches \u2014 but permanent and at the time went largely unnoticed or was passed off as a data glitch. However, University of Chicago geophysicist Sunyoung Park felt the recorded signals that indicated a shift pointed to something tangible. In fact, the ground movement reflected an \u201cextraordinary\u201d and previously undocumented seismic phenomenon, according to a new study<\/a>.\n <\/p>\n \n \u201cWhat was unusual about this movement is basically the whole of Japan was moving nearly uniformly at the same time,\u201d said Park, who led the research.\n <\/p>\n \n She added that the movement, which affected mainland Japan \u2014 Hokkaido to Kyushu \u2014 an area approximately 1,800 miles (3,000 kilometers) in length, did not match the timing of the initial earthquake, and it happened before any significant aftershocks.\n <\/p>\n \n After years of analyzing GPS and seismic data, Park and her colleagues found that waves from the earthquake had traveled down to Earth\u2019s core and then rebounded to the crust, displacing four major tectonic plates.\n <\/p>\n \n While seismologists knew that waves from large earthquakes can travel down through the planet and bounce off its outer core, which is liquid metal, they thought that the energy dissipated before returning to Earth\u2019s crust.\n <\/p>\n \n \u201cThat type of deep-diving wave triggering some kind of event is new, and this event is very unusual, also in the sense that it\u2019s so broad,\u201d Park explained.\n <\/p>\n \n Though earthquakes can cause dramatic ground movement \u2014 tearing ruptures in land and moving larger areas by several inches \u2014 such movement is typically more localized than the country-long seismic event detected by Park and her colleagues.\n <\/p>\n \n Goran Ekstrom, a geophysicist at the Columbia University, said that In the 2011 earthquake, for example, the two plates sliding past each other under Japan moved by some 10 meters, said Goran Ekstrom, a geophysicist at the Columbia University.\n <\/p>\n \n \u201cThis rapid movement is what generated the ground shaking and the tsunami, and it also made the whole island of Honshu shift towards the East by 20 centimeters or so,\u201d Ekstrom, who wasn\u2019t involved in the study, said, referring to Japan\u2019s largest island.\n <\/p>\n \n The displacement Park and her colleagues discovered, while smaller, is noteworthy because it occurred over such a large area, making it the broadest ever recorded, and it released about the same amount of energy as a 7.5 magnitude earthquake, according to a news release<\/a>.\n <\/p>\n![\"People](\"https:\/\/media.cnn.com\/api\/v1\/images\/stellar\/prod\/2011-03-12t120000z-571645156-gm1e73c0s2501-rtrmadp-3-japan-quake.jpg?c=original&q=w_860,c_fill\" "\\"\\"")
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