Kentucky Geological Survey Challenges the Seismic Hazard Map
Researchers at the Kentucky Geological Survey (KGS) at the University of Kentucky say the earthquake hazard maps published by the U.S. Geological Survey, estimating the seismic threat in western Kentucky and the surrounding region, overstate the actual threat. Because they believe the methods used by the USGS to calculate the threat are flawed, KGS researchers have been working for a decade to have the maps changed to reduce the estimated threat level.
The USGS uses a probabilistic method to determine the earthquake hazard level. “This method, mathematically, is not correct,” said Zhenming Wang, head of the KGS Geologic Hazards Section. “The national hazard maps are not scientifically sound, that’s why there is a problem.”
“We do deterministic or scenario analyses for the Paducah region, and our results show a much more moderated seismic hazard,” said KGS Director Jim Cobb. “It’s just not as significant as California and other places like Japan or China.”
Cobb and Wang wrote an article published by the Geological Society of America late last year detailing the scientific flaws in the probabilistic method and presenting the deterministic/ scenario method and its results.
The different seismic threat estimates from the two methods are not purely academic. Cobb points out that standard building codes are based on the USGS hazard maps, and federal installations cannot be constructed in zones with an earthquake threat as high as the USGS map depicts for the New Madrid Seismic Zone, which includes western Kentucky. That can mean western Kentucky could be at an unnecessary disadvantage when trying to attract federal facilities, impeding economic development.
The USGS is developing new hazard maps, which will be released sometime this year. Wang hopes the efforts to persuade USGS will result in a reduced estimation of the seismic hazard in the Midwest on the new maps.