What caused two Japanese islands to drift 10cm apart in days?
Two small islands in Japan’s southwestern Tokara chain have mysteriously moved nearly 10 centimeters apart in just three days.
Kodakarajima shifted 6 centimeters north-northwest, while nearby Takarajima moved 3.5 centimeters south following a magnitude 5.6 earthquake on July 2, according to Professor Ohta Yusaku of Tohoku University.
Using data from the Geospatial Information Authority of Japan and mobile phone base stations, Ohta confirmed that the islands, previously moving northeast together, had suddenly diverged, a phenomenon never seen before in the area.
Surprisingly, Ohta said the quake itself may not have been the direct cause of the shift. "Considering the magnitude and distance from the epicenter, it’s unlikely the quake alone triggered this movement," he explained.
He pointed instead to possible underground forces, such as magma or fluids seeping into the earth's crust, or a slow slip along a shallow fault on the continental plate.
While it's still unclear whether this crustal movement signals a larger quake to come, Ohta said he will analyze historical data to better understand the cause of the phenomenon, NHK World Japan reports.
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