In a world of ever more ubiquitous wireless internet, it’s easy to forget that our ability to get online continues to rely on the laying of miles of fiber-optic cables not just on land but also along the ocean floor. Could these same cables also be used to help detect earthquakes and look at other earth science issues? A new project carried out by researchers at Rice University, UC Berkeley, Lawrence Berkeley National Laboratory, and the Monterey Bay Aquarium Research Institute suggests they could.
In a four-day demonstration, the researchers showed how it was possible to repurpose a 32-mile-long cable, which carries data back and forth in California’s Monterey Bay, to act as a seismology instrument.
“We used a fiber-optic sensing technique to transform a seafloor telecommunications cable, commonly used to connect an offshore science node to land, into a dense seismic array spanning the continental shelf offshore Northern California,” Nate Lindsey, a researcher at the University of California, Berkeley, told Digital Trends. “By using this array to record a local earthquake, we were able to observe a pattern of scattering in the seismic wavefield that is consistent with the presence of multiple seafloor faults, some of which lined up with the locations of known faults, and others which had not yet been identified.”
The researchers on the project employed an approach called Distributed Acoustic sensing, requiring short pulses of light to be sent along the cables. The resulting backscattering effect can then be analyzed to pick up information about topography and seismic activity. This would normally require special seismometers. However, this approach, built around existing infrastructure, may turn out to be significantly cheaper.
“High hazard regions are a priority for the next stages of this research,” said Lindsey, describing the next phase of the project. “Continuing our calibration efforts to understand the potential of this tool will also mean recording with other types and sensors and in other types of marine environments such as the shelf break region at the edge of the continental slope and in the deep ocean.”
A paper describing the work, titled “Illuminating seafloor faults and ocean dynamics with dark fiber distributed acoustic sensing,” was recently published in the journal Science.