Peril of ‘Quicksand’ Phenomenon in Quake Cited

A major earthquake in the central United States will give some soils the consistency of quicksand, toppling even many quake-resistant buildings, officials said Wednesday.

E. Erie Jones, executive director of the Central United States Earthquake Consortium, a seven-state disaster preparedness agency, urged that building codes and land-use regulations be changed to prepare for the liquefaction risks in an earthquake.

New Madrid Fault

“It will probably be worse than the shaking itself,” Jones said during a conference focusing on the New Madrid Fault, which runs from northeastern Arkansas to southern Illinois.

Geologists say that the New Madrid Fault could produce a massive quake that would kill thousands of people and destroy billions of dollars worth of property.

“Liquefaction is a phenomenon that prevails in any earthquake setting,” Jones said. “But, in the Mississippi River Embayment, the whole area is a big bowl of Jell-O.”

Arch Johnston, director of the Tennessee Earthquake Information Center at Memphis State University, said that the entire Mississippi River Valley is at high risk for soil liquefaction in a quake registering 7 or above on the Richter scale.

Jones and Johnston were among panelists at a workshop on earthquake risks that included engineers, scientists, industry representatives and state and local officials.

Johnston said that most of northeastern Arkansas, southeastern Missouri and parts of northwestern Tennessee still show evidence of liquefaction that occurred during earthquakes in 1811 and 1812.

“You get a sand layer, say 10 or 12 meters down,” Johnston said. “In the quake, it will liquefy, and the fine silt on top doesn’t. You have compaction, and that sand is under pressure and it shoots to the surface in the form of a sand geyser. If you have a building on top of it, it’s going to topple over.”

Jones said that building codes should be revised to require quake-resistant structures. Large buildings in areas where the soil may liquefy in a major quake can be constructed on huge concrete rafts that will be stable in a quake, he said.