Nevada's third ranking for large-magnitude earthquakes is pushing earthquake preparedness to the forefront.
"Newcomers to our area are sometimes surprised to learn that the earthquake ground-shaking hazard here is significant," said Barbara Luke, a professor in the Howard R. Hughes College of Engineering. "A major goal of our project is to inform local residents of our seismic risk so they can be prepared."
In Southern Nevada, researchers have identified active faults capable of producing an earthquake of magnitude 6.0 or greater.
UNLV geoscientists recently completed a three-dimensional model that shows how the shallow sediments of the Las Vegas Valley will respond during an earthquake. The model can be used to design safer buildings and highway bridges and will aid in developing a comprehensive seismic hazard map for Las Vegas -- helping local officials in disaster relief planning, land use planning, and assessment of existing infrastructure.
How the Ground Will Respond
Over the last two years, Luke and her team performed site surveys to determine shear-wave velocity, or the speed at which certain stresses move through various sediments. Shear-wave velocity varies according to the type and condition of the material (rock, clay, sand, gravel.) and describes the "stiffness" of a soil.
"Areas with overall lower shear wave velocity would be expected to undergo more severe shaking at lower frequencies, lasting for a longer time, than those having higher velocity," Luke said. "These differences translate to different requirements for structural design across the valley."
The research team used their own field testing and analyzed more than 160 seismic site classifications to compile a database of 230 shear-wave velocity measurements. Using the database along with interpretations of nearly 1,600 geologic well logs, the team created the shear-wave velocity model for the valley to depths of hundreds of feet.
Research a Collaborative Effort
Luke and colleagues Aly Said of the College of Engineering and Wanda Taylor of the College of Sciences were awarded a multiyear grant from the U.S. Department of Energy for their "Earthquakes in Southern Nevada" study.
A more detailed explanation of the project appeared in the November 2008 issue of The Leading Edge, an official publication of the Society of Exploration Geophysicists.