While other UC students and faculty were leaving Japan or canceling trips and study abroad programs last month, UC Davis civil engineering professor Ross Boulanger was headed the other way.

On March 17, the UC Office of the President canceled all nonessential travel to Japan. But with a waiver in hand from UC Davis Chancellor Linda P.B. Katehi, Boulanger departed March 24 for a weeklong trip to examine and document earthquake damage.

Boulanger, who is director of the Center for Geotechnical Modeling at UC Davis, was co-leader of a team of experts organized by the Geotechnical Extreme Events Reconnaissance, or GEER, an international association that quickly gathers and preserves information from earthquakes, tsunamis, hurricanes and other extreme events that can be used to improve our understanding of these disasters.

The team spent a week in the Kanto region east of Tokyo, working with Japanese scientists and engineers. The mostly low-lying Kanto region includes the Tone River, old watercourses and reclaimed land that has been covered by development.

At first glance, the damage did not look dramatic, said Boulanger, who is now back on campus. Houses and light commercial buildings leaned slightly from true, sidewalks had sunk a couple of feet, manhole covers had floated up.

Soil turns to liquid

But the forces that created the damage were powerful: The soil literally turned to liquid during the earthquake shaking, a phenomenon that is typical of fill and young soils.

“In the Kanto region, the shaking was not very high but it was of very long duration,” Boulanger said. The shaking lasted for two to four minutes – compared with 10 to 15 seconds in the 1989 Loma Prieta earthquake.

“Theoretically, we know that longer shaking causes more damage, so this is very useful information,” he said.

Many smaller buildings, such as homes and low-rise commercial buildings, tilted a few degrees as the soil softened beneath them. They avoided structural damage, Boulanger said, because of the reinforced concrete mats with deep grade beams that the Japanese commonly use as building foundations. So the houses tipped, rather like boats on a frozen ocean.

But while the homes were intact, they lost gas, water and sewer connections, rendering many of them uninhabitable. Utility lines were also damaged, because the trenches that housed them were filled with loose backfill that liquefied easily.

In some neighborhoods, Boulanger said, the authorities ran temporary gas lines and installed public water taps in the street.

“The damage may not look big, but pervasive liquefaction is very difficult to recover from,” Boulanger said.

The sharing of GEER data

The data collected by GEER members is shared throughout the geotechnical engineering community, allowing engineers to refine their computer models of soil movement and liquefaction and design new experiments for simulation devices, such as the giant centrifuge at the Center for Geotechnical Modeling or the shake table at UC San Diego.

Japan has an excellent network of ground motion sensors, and the recordings from those instruments will be a valuable source of information alongside the field observations, Boulanger said.

“In the field, you can see complexities that you wouldn’t expect in a numerical simulation,” he said.

Data collected on the ground also supplement that collected from aircraft and satellite imagery, which can now be modeled in three dimensions at UC Davis' Keck Center for Active Visualization in Earth Sciences.

“There are some things you just can’t see from the air,” Boulanger noted. For example, during this trip, the team was able to go underground to inspect a water treatment plant.

“The real world provides a test with geologic complexity, natural processes of cementation and aging, and the effects of construction techniques,” Boulanger said. Those case histories will help researchers improve their understanding of earthquakes and how to mitigate their effects.

Eyewitness accounts

Being on the ground also provides opportunities to talk to people who were there during the earthquake.

“Sometimes you’ll be looking at a building and the owner or tenant will come out and they’ll tell you what happened, what the shaking was like,” Boulanger said. “You can learn as much from talking to people as you can from images.”

Until now, the scientists have stayed out of the areas worst affected by the tsunami — humanitarian aid should come first, Boulanger said. However, a GEER team is due to begin work in the devastated Sendai area this month, he said.

Boulanger also had an opportunity to see the disaster’s toll at the personal level. Japanese earthquake scientists felt dismay and sadness over the scale of the disaster, as well as unease over the continuing problems at the Fukushima nuclear plant, he said. They were sensitive to the need to prioritize aid over science in the Sendai region, and willing to accept power cuts and other inconveniences without complaint.

“The Japanese value politeness and civility, and they continue to show that,” he said.

“They know it’s really setting them back, but at the same time, they see that it’s a time to learn as much as they can and they are working really hard to do that,” Boulanger said.