This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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. Using existing fiber-optic telecommunications cables buried just a few feet below the ground under Penn State's University Park campus, the researchers developed a new way to use distributed acoustic sensing technology, or DAS, to better understand how atmospheric acoustic waves transfer energy into the ground.
They also demonstrated how this coupling can be used in seismic imaging. Their findings were published today (Aug. 21) in Science Advances. "Thunder generates atmospheric acoustic waves that couple into the ground, producing seismic signals," said Tieyuan Zhu, associate professor of geosciences at Penn State and corresponding author on the paper.
"We demonstrated the first successful seismic imaging using thunderquakes. Not only does this research serve as a proof of concept for using thunderquakes as seismic sources for tomography, but DAS provided a new way to observe the interaction between the atmosphere and the solid Earth." To assess seismic events near Earth's surface, researchers use an approach called seismic tomography, which can produce an image of the subsurface from waves recorded by sensors at the surface. In this study, the waves used for imaging were acoustic waves produced by thunder rather than by earthquakes or active seismic equipment.
"Seismic tomography is important because it helps us understand what is happening beneath the surface," said Zhu, who is also a faculty affiliate with the EMS Energy Institute. "Seismic imaging can be used to evaluate additional geohazards like sinkholes or landslides, assess groundwater and mining resources and study volcanoes and magma pockets. Only tomography can give us information about the Earth's subsurface structure that we often cannot observe directly." Seismic imaging is traditionally done with expensive tools that require human deployment or with passive surveys that rely on seismic sources, like those generated by earthquakes.
These passive seismic methods generally require a robust monitoring array, but the thunderquake method allows for passive imaging in places with fewer earthquakes, like the central and eastern United States. The method of using existing fiber-optic cables also allows for easier imaging in less accessible locations, such as in the Arctic or highly regulated urban areas, with minimal disruption to the environment and infrastructure, the researchers said. In this study, the researchers shot a laser beam down a preexisting 2.5-mile (4-kilometer) fiber-optic telecommunications cable buried beneath the University Park campus and recorded how the phase of the backscattered light shifted because of tiny strains along the fiber caused by seismic waves moving through the ground.
Lead author Nolan Roth, who conducted this research as part of his doctoral studies at Penn State and is now a postdoctoral researcher at The Ohio State University, said people have tried to use thunder for seismic imaging in the past, but it's been difficult because the process is so complex. "Without incredibly high-resolution sensing, it's difficult to actually piece together what's going on when the thunder hits the ground," Roth said. "With DAS, we are recording hundreds of samples every second and every few meters along the cable.
Extract — continue reading at the source.
