Ground Beneath Japan Still Hasn't Settled Since the Sendai Earthquake

The Great East Japan Earthquake in March 2011 rocked the island country for 6 full minutes, wreaking devastation that is still being cleaned up, cleared away and paved over today. But even as structures are rebuilt, roads are re-paved and power lines restored, there's a deeper, and potentially more damning problem looming beneath the surface in cities bordering Tokyo Bay: soil liquefaction.

Liquefaction occurs when sediment in the ground becomes so saturated with water that it begins ebbing and flowing, sometimes opening up trenches in the surface that can fell entire apartment buildings. It's known to happen after earthquakes, when the vibrations in the Earth's crust create separations in packed soil, effectively freeing it up to begin moving and sliding.

The ground in parts of the east side of Honshu, near the Sendai earthquake's epicenter, hasn't settled yet. The results are trippy–not to mention dangerous–experiences for Japanese city dwellers. Imagine you're strolling down the sidewalk in downtown Chiba and a strip of asphalt to your left, maybe 100 feet long and seven feet wide, begins sliding back and forth all by itself.  Then water begins gushing up from the cracks in the ground, flooding the street in front of your eyes.

The Tokyo Metropolitan Government recently simulated the long-term effects of a large earthquake and concluded that 22 percent of Tokyo's metropolitan area–about 270 square kilometers–could be in danger of liquefying. Liquefaction has impacted 37,000 households in Urayasu, in Chiba prefecture (not far from Tokyo), according to The Mainichi, one of Japan's largest newspapers.

The earthquake and ensuing liquefaction was so jarring that it warped 86 percent of the city's property lines. Now they have to be redrawn, a process the local government hopes to sort out by 2016. What that means for residents is that they can't sell their homes—no one knows where their property begins or ends. An official in the city's road department said roads in some places are between 10 and 20 centimeters off the initial survey markings.

It's kind of like the problem Florida is facing with its endemic sinkholes, only in reverse. In Florida, ground well pumping combined with a lasting drought is drying up the state's aquifers and leaving massive empty caverns that grow upwards, toward the the surface on which we walk and live. Sometimes one of those caverns breaks through the ground and swallows a home (and, recently, a person along with it).