COLUMBUS (WCMH) — The magnitude-9.0 earthquake and subsequent tsunami that devastated parts of Japan on March 11, 2011, killing 16,000 people, was foreshadowed by a series of “wobbles” detected by a GPS seismic data network.
OSU Earth Sciences professor Michael Beavis published a new study in Nature (April 30), based on the work of a team of researchers that mapped data obtained from 1,000 GPS monitors scattered across Japan. Land mass movements were detected of to 4 to 8 millimeters during a period of about six months. The motions were not consistent with normal cyclical movements and would not have been noticed by anyone on the island.
“First you see Japan moving to the east, then you see it move to the west, and then it moves to the east again–and then you get the big earthquake,” Beavis said. He likened the land mass “wobbles” to a car on a highway being buffered by crosswinds.
Beavis believes the research findings could be applied to predicting the potential risk of future earthquakes common in subduction zones, when a slab of the earth is being thrust under another plate along the margin where the subterranean pieces of earth collide. The release of frictional stress that results in an earthquake is akin to a rubber band pulled to the breaking point and snapping back, much as the earth vibrates violently along a fault zone.
Continental and oceanic plates meet in several areas in the Japanese archipelago. Earthquakes below and near the ocean raise the risk of a deadly tsunami, or tidal wave. The March 2011 Tohoku earthquake, the largest ever recorded in Japan, also damaged several nuclear reactors.
The tsunami triggered by the very large earthquake caused massive destruction along coastal sections of Tohoku and southern Hokkaido, and was responsible for most of the deaths. The waves surged up to an astounding 128 feet above sea level at Miyako city and traveled 6 miles inland, flooding about 217 square miles.