By Mark Wilson
Evansville Courier Press

EVANSVILLE, Ind. — Next year, local officials will have a new tool to plan emergency responses to an earthquake in the Evansville area.

The U.S. Geological Survey has been working with officials and university researchers in Indiana, Kentucky and Illinois to survey the soils in the Evansville area and create a series of earthquake hazard maps.

Evansville was targeted because of its location in both the Wabash Seismic Zone and the area that would feel a strong impact from a large quake from the New Madrid fault zone to the south. A similar project has been completed in Memphis, Tenn., and is under way for the St. Louis area.

Oliver Boyd, a U.S. Geological Survey geophysicist heading the project, hopes the maps are ready for public use by June 2009. The project has taken years to complete and cost an estimated $300,000. The maps and information will be available on the Internet for anyone.

Geologists who have been working on the project answered questions during a forum Wednesday at Evansville Central Library hosted by the Southwestern Indiana Disaster Recovery Business Alliance.

Researchers have analyzed hundreds of soil borings from the area to understand the types of soils beneath the area's buildings, roads and other infrastructure.

By knowing what those soil types are and how deep they are, Jennifer Haase, an assistant professor of earth and atmospheric sciences at Purdue University, said researchers can determine how the ground will shake during a quake. They also can predict the possibility of soil liquefaction, which would cause the ground to no longer support the weight of buildings and structures, leading to collapses.

What the study found was that soils closer to the Ohio River are more likely to cause buildings to sway from the force of ground shaking and are also highly susceptible to liquefaction. Some soils farther away from the river are likely to cause structures, especially low-lying buildings, to shake more violently.

"We want to make sure we are not building in those areas or that we are building properly," Haase said. "The better our information about what is below the surface, the better our estimates of what the earthquake hazards are."

While the earthquake hazard maps would be useful for planning and zoning, she said they are not intended to take the place of specific site studies for construction.

They also would be useful for developing plans about what bridges, infrastructure and buildings should be inspected for damage first in the aftermath of an earthquake.

Sherman Greer, executive director of the Evansville-Vanderburgh County Emergency Management Agency, said the maps would help emergency officials determine how to plan for deploying their resources in the case of an earthquake.

Christine Martin, director of the disaster recovery business alliance, said a seminar for contractors and engineering companies might be held next year to discuss how they can use the maps.

Copyright 2008 Evansville Courier Press