Thunderquakes enable seismic imaging of Earth's shallow subsurface

Thunderquakes, the seismic signals generated by thunderstorms, have been harnessed as a novel tool for imaging Earth’s shallow subsurface, marking a breakthrough in geophysical research. A team of scientists led by Tieyuan Zhu, an associate professor of geosciences at Penn State, has successfully demonstrated the potential of these atmospheric acoustic waves to provide detailed images of underground structures. Published in Science Advances on August 21, their work outlines a method that uses existing fiber-optic cables to detect and analyze thunderquakes, offering a cost-effective and environmentally friendly alternative to traditional seismic techniques. The study focused on the University Park campus, where a 2.5-mile-long fiber-optic cable, originally installed for telecommunications, was repurposed as a sensor network. By employing distributed acoustic sensing (DAS) technology, the researchers captured minute changes in the fiber’s physical properties caused by seismic waves traveling through the ground. These waves originate from thunderclaps, which generate low-frequency acoustic pulses that travel through the air and eventually transfer energy into the ground, creating detectable seismic signals. The ability to track this transition from atmospheric sound to ground motion represents a key innovation in the field of geophysics. Traditional seismic imaging relies on either expensive, manually deployed instruments or passive methods that depend on natural seismic activity, such as earthquakes. However, these approaches face limitations in regions with limited seismicity, such as the central and eastern United States, where earthquake activity is relatively sparse. The thunderquake method overcomes this challenge by utilizing the consistent occurrence of thunderstorms, which can be frequent even in non-seismic zones. Moreover, the use of existing fiber-optic infrastructure eliminates the need for extensive setup, making it particularly useful in remote or heavily regulated environments like the Arctic or urban centers. Nolan Roth, lead author of the study and currently a postdoctoral researcher at The Ohio State University, emphasized the complexity of previous attempts to use thunder for seismic imaging. “Without incredibly high-resolution sensing, it's difficult to actually piece together what's going on when the thunder hits the ground,” he explained. With DAS, the team achieved unprecedented detail by recording hundreds of data points per second along the fiber, enabling them to map the transformation of atmospheric acoustic energy into seismic waves with remarkable precision. This level of accuracy had previously eluded researchers working with similar methods. The implications of this discovery extend beyond academic curiosity. Improved understanding of how energy transfers between the atmosphere and the solid Earth could enhance our ability to monitor geohazards such as sinkholes and landslides. It also offers new insights into resource assessment, including groundwater and mineral deposits, as well as volcanic and magmatic activity. According to Zhu, the technique provides a unique opportunity to explore the dynamic interactions between Earth’s surface and its atmosphere, potentially leading to more accurate models of subsurface behavior. As the research moves forward, the team plans to expand their experiments to other locations with varying geological conditions, aiming to validate the reliability of the thunderquake method across different environments. The integration of advanced fiber-optic networks with geophysical analysis opens up exciting possibilities for future exploration, demonstrating how emerging technologies can transform our understanding of the planet.