NEW YORK, October 3, 2025: Researchers at Pennsylvania State University have demonstrated that existing fibre-optic cables, commonly used in telecommunications infrastructure, can be repurposed to detect underground geohazards such as sinkholes with a high degree of accuracy. The study, published in the Journal of Geophysical Research: Solid Earth, outlines a new method of subsurface monitoring that could significantly improve early warning systems for ground instability. The team used a distributed acoustic sensing (DAS) system connected to four miles of existing fibre-optic cable buried beneath the university’s campus.
The DAS unit transmits light pulses along the cable and measures the light that is reflected back due to ground vibrations. These reflections enable researchers to detect changes in the subsurface, including fractured zones and potential voids, by analyzing variations in seismic wave speeds. The approach relies on ambient noise generated by everyday sources such as pedestrian traffic and vehicles. By applying cross-correlation techniques to these vibrations, the researchers converted them into usable seismic data. The result was a high-resolution map of seismic surface wave velocities along the length of the cable, allowing detection of anomalies hundreds of feet below the surface.
In the course of their analysis, the researchers identified a region beneath the campus where seismic waves slowed significantly, indicating a potential subsurface void or weakened zone. While no immediate structural threat was confirmed, the finding supported the system’s effectiveness in detecting potential geohazards using infrastructure already in place. Conventional geophysical tools, such as geophones, require individual installations and deliver limited spatial data. These systems are also expensive and labour-intensive. In contrast, the fibre-optic DAS system provides continuous monitoring across long distances without the need for new underground equipment.
Infrastructure reuse lowers costs of seismic monitoring
This advantage makes it a more scalable and cost-effective method for monitoring ground stability in both urban and rural settings. The research forms part of a broader project named FORESEE (Fiber-Optic foR Environmental SEnsEing), aimed at developing environmental monitoring applications using existing fibre networks. The project is supported by the National Science Foundation and involves collaboration with multiple municipal authorities. Upcoming deployments are planned in urban settings, including Pittsburgh, where researchers intend to integrate the system into metropolitan infrastructure to study its performance in dense, real-world environments.
One of the limitations acknowledged by the research team is that the sensitivity of fibre-optic cables depends on how well they are coupled with surrounding soil or rock. Additionally, the system primarily detects vibrations along the direction of the cable, which may affect its ability to sense vertical or perpendicular ground motion. Despite these technical constraints, the technology has shown reliability in capturing relevant seismic signals and producing actionable data. The findings arrive at a time when infrastructure resilience is a growing concern due to increasing incidents of ground subsidence and sinkhole activity in various parts of the world.
By converting dormant or underutilized fibre-optic cables into dense sensor arrays, researchers believe the approach can enhance existing geological monitoring networks without the need for extensive new infrastructure. The study was led by Tieyuan Zhu, associate professor of geophysics at Penn State, who noted the effectiveness of using what was traditionally considered noise as a data source. The system offers a new way to monitor ground stability using infrastructure already embedded in the built environment, potentially transforming how early warnings for subsurface hazards are delivered. – By Content Syndication Services.