Thunderstorms cause a lot of commotion in the atmosphere, but their impact actually runs much deeper than expected. That's because they can produce seismic “thunderquakes,” which aren’t nearly as destructive as they sound; in fact, these quakes are helping researchers see how the Earth looks below the surface.
A thunderquake occurs when lightning strikes the ground, generating acoustic shock waves — in other words, thunder — that then spread beneath the surface. This phenomenon has been observed in the past, but a new study published in Science Advances has discovered that thunderquakes can act as a valuable source for seismic imaging, showing what’s happening underground as the shock waves interact with existing fiber-optic telecommunication cables.
“Our research shows that thunderquakes can act [as] a new source for near-surface seismic imaging, especially in regions with limited access to traditional seismic sources,” said study author Tieyuan Zhu, a professor of geosciences at Pennsylvania State University, in a statement.
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Seismic Activity From Thunderquakes
To survey what’s going on underground, scientists often rely on seismic tomography, an imaging technique that uses seismic waves.
“Seismic imaging can be used to evaluate additional geohazards like sinkholes or landslides, assess groundwater and mining resources, and study volcanoes and magma pockets,” said Zhu. “Only tomography can give us information about the Earth’s subsurface structure that we often cannot observe directly.”
Explore All OptionsNormally, the seismic waves that scientists use for this technique come from earthquakes or human-made sources like controlled explosions. However, atmospheric influences, like changes in air pressure or thunderstorms, can also create seismic waves, but how energy disperses from the atmosphere into the ground is poorly understood, according to the new study.
Capitalizing on Fiber-Optic Cables
Researchers have now found that thunderquakes can be applied to seismic tomography with the help of distributed acoustic sensing (DAS), which involves detecting vibrations along optical fibers.
For the study, the researchers shot a laser beam down an approximately 2.5-mile-long preexisting telecommunications fiber-optic cable buried beneath Penn State University’s campus. For over two years, sensors on this cable detected 458 thunderquakes, each one producing seismic waves that induced tiny strains along the fiber.
“This allowed us to see what was going on in that transition from atmospheric acoustic source to a seismic signal in very high resolution, which is something that nobody else has been able to do while looking at thunder,” said lead author Nolan Roth, a postdoctoral researcher at Ohio State University.
The DAS method captured crucial seismic waves called air-coupled Rayleigh waves, which researchers can use to study the subsurface as far as 300 feet below the surface.
Knowing how thunderquakes work, they say, will help them gain insight into the interactions between the atmosphere and Earth’s surface.
“Understanding this coupling will allow cross-disciplinary researchers to answer questions in both geosciences and meteorology,” Roth said.
Seismic Applications on Earth and Beyond
Thunderquakes could potentially open unprecedented seismic imaging opportunities in areas that don't experience many earthquakes, like the central and eastern U.S., where there are tens of millions of lightning strikes annually.
Another benefit of using thunderquakes for seismic imaging is the abundance of fiber-optic cables, especially in urban areas. However, fiber-optic cables are also present in less accessible areas like the Arctic, making it possible to expand the range of seismic imaging. Since climate change is projected to increase lightning activity by up to 50 percent by 2100, according to the study, thunderquake imaging could become more accessible as time goes on.
Thunderquakes may even have applications beyond Earth; they could provide an alternative way to study quakes on other planets and moons that also experience thunder-induced seismicity. Whether or not this will prove useful in outer space remains unknown for now, but either way, the researchers conclude that thunderquakes represent an exciting new avenue to monitor seismic waves.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Science Advances: Imaging Earth’s subsurface with thunderstorm-generated seismic waves
