Implosion of a cooling tower showed the sensitivity of KGS seismic monitoring network
What does the intentional collapsing of a water-cooling tower at an eastern Kentucky power plant have to do with an earthquake monitoring network operated by the Kentucky Geological Survey? For one thing, the implosion of the tower at American Electric Power’s Big Sandy Power Plant in September created a ground-shaking event of a size roughly equivalent to a magnitude 1.5 earthquake. (You can watch on YouTube as the implosion created the seismic event.)
Sensitive instruments in the KGS Eastern Kentucky Microseismic Monitoring Project recorded the event, which isn’t surprising. “We set up this network during the past year and a half to monitor background, low-level seismic activity in that region and also to help distinguish between naturally occurring events and those that are caused by human activity,” says network manager Seth Carpenter, of the KGS Geologic Hazards Section.
KGS wanted to be ready to monitor possible ground movement caused by the injection of fluids related to future oil and gas activities in the region. Oil and gas drilling operations, and the resultant disposal of wastewater via subsurface injection, are expected to increase with the discovery of the resources in the Berea Sandstone and Rogersville Shale plays. In other parts of the United States, such activities have been linked to recent earthquakes that have caused damage to structures and infrastructure in some cases.
When a KGS staff member came across the YouTube video of the Sept. 24 destruction of the cooling tower in Louisa, he asked whether it might have been recorded by the instruments in eastern Kentucky. Carpenter analyzed the network recordings for that day and found that five of the 13 stations in the network recorded the event clearly. Using the seismic-wave arrival times as observed on seismograms from these five stations, he located the epicenter of this magnitude 1.5 event in Lawrence County. The location was about 350 meters from where the structure stood until its implosion. "It’s good to know that we have enough high-quality seismic stations operating in the network to calculate the location of a small event with this kind of accuracy," says Carpenter. "This increases our confidence that we will be able to identify the locations and nature of events that are recorded by the network."
At present, no earthquakes—induced or natural—have occurred within the monitoring project area, the Rome Trough fault zone of eastern Kentucky. The network has recorded 46 earthquakes in the surrounding region, however. During the same period, the network has also recorded more than 650 mine blasts per month, as well as hundreds of earthquakes from around the world.