What do you do when apparently solid ground in a matter of minutes turns into a soft and slick swamp? How do you quickly evacuate a wide, low-lying area near the ocean when streets and highways have broken apart and are tilting at crazy angles?

Liquefaction is an aspect of the Japanese and New Zealand earthquakes that has been under-reported. It is a phenomenon with enormous significance for the Pacific Northwest, especially for low-lying coastal areas of Pacific County.

Many of us live atop what amounts to a vast bowl of muddy Jell-O.

The long duration of subduction zone earthquake causes water-saturated soils to lose their stability. Grains of sediment shift around and large quantities of watery mud known as sand boils flow out onto the surface. Heavy manmade objects like buildings and highways may sink or tilt by several inches or even a three or four feet as the underground finds a new equilibrium. 

Water-saturated could be our official regional motto. The Long Beach Peninsula, Clatsop Plains, Seaside and countless filled-in areas from Ilwaco to Portland are all comprised of sediments floating atop a high water table. 

In a multiple-minute earthquake, highways will form impassable cracks, utility poles will tilt or fall, and even well-constructed buildings may partially sink into the ground. 

Entire structures were tilted and sinking into the sediments, even while they remained intact, Oregon State University Professor Scott Ashford reports about Japan. The shifts in soil destroyed water, sewer and gas pipelines, crippling the utilities and infrastructure these communities need to function. We saw some places that sank as much as four feet.

To see liquefaction in action, search youtube and youll find a variety of vivid examples. This is a good one compiled by Ashford: www.youtube.com/watch?v=GviJkVEMfwQ.

According to OSU, anything near a river and old flood plains is a suspect for liquefaction. The Oregon Department of Transportation has already concluded that 1,100 bridges in the state are at risk from an earthquake on the Cascadia Subduction Zone. Fewer than 15 percent of them have been retrofitted to prevent collapse. Our pipes and many buildings also are at high risk.

Some damage may be reduced or prevented by different construction techniques or retrofitting, Ashford said. The OSU College of Engineering says another reasonable goal is to at least anticipate the damage to know what will probably be destroyed, make contingency plans for what will be needed to implement repairs, and design ways to help protect and care for residents until services can be restored.

In terms of emergency planning, well-intentioned efforts that aim to evacuate residents of low-lying areas by motor vehicles may be doomed to irrelevance. Liquefaction means that literally running for the hills immediately after any serious quake probably is our most-reliable plan.

While our area finds ways to construct the artificial evacuation berms suggested by researchers, establishing and maintaining well-compacted footpaths to high ground could be an affordable interim step.