Geotechnical Lessons from the Tohoku Earthquake

Japan landslide area

Rockslide (background) and flood protection (foreground) in Ishinomaki City, Japan (Photo: Dave Swanson, Reid Middleton)

The magnitude 7.3 earthquake that struck Japan six days ago is a reminder of the more devastating magnitude 9.0 earthquake that struck March 11, 2011. In an earlier post we mentioned a reconnaissance team that traveled to Miyagi Prefecture in Japan in May 2011 after the earthquake and tsunami.

In the landslide area photo above from 2011, the light colored rock slope failed even with reinforcement that protected the slope to the left. The entire land area settled, which allowed Tsunami and high tide water access to the shoreline. Fortunately, in this area the Tsunami water was not as high as other areas, so the buildings weren’t washed away. Blue tarp temporarily protects the river bank from overtopping at high tide.

Doug Lindquist of Hart Crowser had these observations about the geotechnical damage:
Damage generally happened in known geologic hazard areas (tsunami zones, areas near past landslides, liquefiable areas, and reclaimed land).
• Liquefaction damage was extensive even 150 kilometers away from the fault rupture. (Seattle is about 100 kilometers from the Cascadia Subduction Zone.)
• Ground improvement measures are effective.
• Engineering methods can reasonably estimate the liquefaction hazard.
• Newer structures performed well when designed considering known geologic hazards.

As the reconnaissance team report reminds us, a similar earthquake will happen along the Cascadia Subduction Zone, off the coastline from northern California to British Columbia. The impacts of this event on our communities and industry will depend on the actions we take now to prepare for it. The lessons learned from Japan can be applied in our own communities.

For more details on the reconnaissance team’s findings, along with some fascinating photographs, see the report here.

Driving on Styrofoam, Building on Pillows

Geofoam at SR 519

Geofoam at SR 519

You may have seen this recent blog headline: In New York, Buildings ‘Sleep’ on These Giant Red Pillows. Since that headline was called out in an engineering-related notice, you might have assumed it had something to do with seismic stability or that it was related to geotechnical engineering. After all, a recent Washington State Department of Transportation project (SR 519) used giant blocks of styrofoam in the foundation for access ramps and pedestrian areas.

To be more specific, SR 519 had the first application of geofoam approved by the Seattle Department of Transportation. Geofoam, or lightweight expanded polystyrene, is essentially a type of Styrofoam, and is used as lightweight fill in areas where heavier materials would be problematic. For the SR 519 project, using Geofoam helped protect hundred-year-old utilities. Meanwhile, highrises now can have huge rubber or fluid-filled shock absorbers, or Teflon-coated pegs.

But if you clicked on that blog headline about pillows expecting to see an earthquake engineering technology, you would have been delightfully wrong. The blog entry is about a stunning art installation, not about engineering. Although you might wonder whether there is an underlying truth to the art.

Take a look.

Lessons from the Great East Japan (Tohoku) Earthquake

Group at Tsunami Site

Reconnaissance Team in front of Disaster Prevention Building (destroyed by the Tsunami rather than the earthquake). Photo: Mark Pierepiekarz, MRP Engineering

The Tohuku Earthquake was the fourth largest ever recorded in the world.  Doug Lindquist of Hart Crowser was part of a reconnaissance team that traveled to MiyagiPrefecture in Japan last June after the earthquake and tsunami. Doug found the experience in the tsunami-impacted areas profoundly moving.  “The damage was incomprehensible. Nearly everything was gone.”

The goal of the team was to learn lessons to apply to the Pacific Northwest, Alaska, and Hawaii. After all, with the Cascadia Subduction Zone just off the Pacific coast, the Big One around here may not be far off.

 A quick list is of the team’s findings is below. 

  •  Japan is the most prepared country in the world for both earthquakes and tsunamis.  We should continue to look at their examples to save lives and property in our own areas. 
  • Seismic retrofit and protection technology works.
  • CurrentU.S. building codes and standards for earthquake design of new structures are very good at addressing life-safety.
  • For a large earthquake, saving lives is not enough.  Building and infrastructure performance levels need to be higher so people can remain in buildings and the economy can recover quickly.