USGS study finds fiber-optic cables detect earthquake magnitude in seconds
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Researchers from the U.S. Geological Survey and Cal Poly Humboldt discover that fiber-optic cables can estimate earthquake magnitude within four seconds of initial shaking, according to a study published Wednesday. The finding could strengthen early warning systems, providing faster alerts to trigger safety measures like slowing trains and shutting off gas lines.
Fiber-Optic Sensing
The technique, called distributed acoustic sensing, transforms existing telecom cables into dense networks of earthquake detectors. When seismic waves move through the ground, they alter how light travels through the fiber, creating measurable signals. This allows scientists to use cables already crisscrossing the seafloor, expanding monitoring to offshore areas where conventional sensors are scarce and expensive to install.
Machine Learning Training
The researchers trained a machine-learning model on real seismic data from California earthquakes between magnitudes 3.5 and 7.1. Smaller and larger quakes produce distinct energy patterns, and the system learned to recognize these signatures. Tested on a fiber-optic cable in Arcata and Eureka in Northern California, the model accurately estimated magnitude using only the first four seconds of wave arrivals.
Early Warning Enhancement
Current early warning systems rely on sparse seismometer networks, which can take precious seconds to triangulate an earthquake's size. Fiber-optic sensing could provide near-instantaneous magnitude estimates, potentially adding critical seconds of warning. Alerts could automatically slow trains, shut off gas lines, and notify the public via mobile phones.
What's Next
The USGS and Cal Poly Humboldt plan to expand testing to other fiber-optic cables across California and possibly offshore. However, it remains unclear how the technology will perform with the very largest earthquakes or in real-time operational settings.
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USGS study finds fiber-optic cables detect earthquake magnitude in seconds
