Scientists use thunder-triggered vibrations to map what lies underground
US researchers used fiber-optic cables to detect tiny ground vibrations caused by thunder, creating underground maps in the process. The method could offer a cheaper way to spot hazardous underground spots in the future.
Thunder is known for its loud rumble, but the sound waves it produces also trigger extremely small vibrations in the ground, which scientists call "thunderquakes." Researchers have now put this phenomenon to an unusual use — getting a glimpse of what lies beneath the earth's surface.
According to Science Direct, researchers in the United States used fiber-optic cables to detect these vibrations. Such cables are normally used for internet and telecommunications, but it turns out they can also serve as highly sensitive sensors for detecting ground movement.
Over 450 vibrations recorded in two and a half years
Over the course of a two-and-a-half-year study, scientists recorded more than 450 vibrations caused by thunder. They then used this data to build a map showing what lies roughly 100 meters below the surface. The maps revealed several weak spots in limestone layers where sinkholes could potentially form in the future.
How the method works
The principle is fairly simple: when the ground moves even slightly, the fiber-optic cable stretches a tiny amount as well, which changes how light travels through it. By detecting these changes, scientists can determine that a vibration has occurred.
The advantage of this method is that no new, costly sensors need to be installed — existing but unused fiber-optic cables, known as "dark fiber," can be repurposed for the task.
Researchers believe this approach could eventually become a cheaper way to study underground structures and identify potentially dangerous areas before problems arise.
