UC Davis team studies liquefaction in Japan

DAVIS, Calif

"I'm a member of an organization, the Geotechnical Extreme Events Reconnaissance Organization," said U.C. Davis Professor Ross Boulanger, Ph.D.

Boulanger recently led a team of researchers in Japan, looking at how the dramatic earthquake compromised the ground in neighborhoods around Tokyo.

The main culprit is liquefaction -- the same phenomenon that caused so much damage and sparked a huge fire in San Francisco's Marina District during the 1989 Loma Prieta earthquake.

"That's the soil taking on the appearance of a liquid. It's weak and soft at that point. That's why structures can move and deform on it," said Boulanger.

Boulanger took some photos in the Kanto plains region north of Tokyo. They show tanks that floated to the surface, roads that sank, structures left leaning as much as 3 degrees and others that settled well below ground level.

"The serious problem in some of these areas is the fact it breaks all the utilities, everything that is underground. So you have thousands of homes with no gas, no water and no sewer," said Boulanger.

At U.C. Davis, researchers use a giant centrifuge to replicate the stresses to soil that take place during a large earthquake.

"One of the things that we've studied quite a bit is remediation methods, how to make the ground not liquefy. In the centrifuge we build a model that we know will liquefy and then we'll treat it in the way we would see in the field...and see if that works," said U.C. Davis Researcher Dan Wilson.

Researchers take the results of their experiments and combine them with the data from real-life disasters like the one in Japan, where the earth shook for about two minutes.

"We're going to learn a lot about how that long duration of shaking effects the movement of the ground and how it effects both the structures as well as the underground utilities," said Boulanger.

And the lessons are just beginning. U.C. Davis researchers will study the earthquake in Japan, for many years to come.

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