Thunderstorms Reveal What's Beneath the Ground, Penn State 'Thunderquake' Study Finds

Seismic waves produced by thunderstorms, called thunderquakes, can be used as a novel source for seismic imaging, according to a new study led by researchers at Penn State, published in Science Advances.

Using existing fiber-optic telecommunications cables buried just a few feet below the ground under Penn State's University Park campus, the researchers used a technology called distributed acoustic sensing (DAS) to better understand how atmospheric acoustic waves from thunder transfer energy into the ground, and to demonstrate how that coupling can be used for seismic imaging — a method called seismic tomography that produces images of the subsurface from waves recorded at the surface. "We demonstrated the first successful seismic imaging using thunderquakes," said Tieyuan Zhu, associate professor of geosciences at Penn State and corresponding author.

The researchers shot a laser beam down a 2.5-mile (4-kilometre) buried fiber-optic cable and recorded how the phase of the backscattered light shifted due to tiny strains along the fiber caused by seismic waves. "With DAS, we are recording hundreds of samples every second and every few meters along the cable," said lead author Nolan Roth, who conducted the research as a Penn State doctoral student and is now a postdoctoral researcher at Ohio State University. Unlike traditional seismic imaging, which relies on expensive equipment or earthquake-generated waves, the thunderquake method allows passive imaging in places with fewer earthquakes, such as the central and eastern United States, using cables already in place.

Seismic tomography can be used to evaluate geohazards such as sinkholes or landslides, assess groundwater and mining resources, and study volcanoes and magma pockets, according to Zhu, who is also a faculty affiliate with the EMS Energy Institute.