Good news! Amazing stuff!
"Researchers from Nokia Bell Labs [and Seismics Unusual] have figured out how to use seafloor telecom cables as earthquake detectors, using the existing fiber-optic network to record real seismic events. While the system isn’t yet used for routine monitoring or early warning, the proof-of-concept shows that today’s global cable network could double as a dense, low-cost sensor array for offshore earthquakes and tsunamis."
From the abstract:
"The global telecom network's ~1.5 million km of submarine fiber offers a vast opportunity to instrument currently unmonitored ocean regions.
These submarine cables are particularly valuable for addressing the scarcity of deep ocean geophysical data.
While Distributed Acoustic Sensing (DAS) is a powerful technology, its large-scale use on active telecom fibers faces two critical challenges.
First, most DAS systems require dark (unused) fibers, which are scarce and costly. More critically, standard DAS cannot sense past the optical repeaters spaced every 50-80 km along trans-oceanic cables, limiting observations to the first near-shore segment.
First, most DAS systems require dark (unused) fibers, which are scarce and costly. More critically, standard DAS cannot sense past the optical repeaters spaced every 50-80 km along trans-oceanic cables, limiting observations to the first near-shore segment.
Overcoming these barriers is essential for unlocking basin-scale sensing.
Here we present recent advancements in distributed fiber sensing across the entire length of active submarine telecommunication cables.
We demonstrate a DAS system based on optical frequency domain reflectometry achieving 50m spatial resolution >1000km offshore in water depths exceeding 1000m. This enables high resolution detection and analysis of teleseismic body waves and environmental signals in the deep ocean. This proposed sensing system is fully compatible with existing telecom traffic, allowing for large-scale deployment without the need for dark fibers.
Given the scarcity of prior DAS measurements in this environment, we compare our results to standard DAS measurements on shore-spans and simultaneously acquired per-span interferometry data from the same cable. While per-span data is more established, its resolution is fixed by repeater spacing, typically 50-100km in telecom cables.
Our findings demonstrate a viable pathway to transform trans-oceanic telecommunication cables into basin-scale seismic and oceanographic observatories, opening a new frontier for Earth monitoring."
From the preprint abstract (one of the shortest abstracts I have seen in a while and the paper has only 4 pages):
"We detect the recent M8.8 mega-earthquake in Eastern Russia, on a 4400km long active telecom cable in the Pacific Ocean. The resolution achieved 100m represents the highest spatial resolution, the largest number of ocean-bottom sensors, and the first fiber-optic deep-ocean observation of a tsunami wave."
S13A-02 Overcoming the Repeater-Induced Reach Limitation: High-Resolution Continuous DAS on Active Trans-Oceanic Cables (Invited) (no public access)
Submarine Cable Deep-Ocean Observation of Mega-Thrust Earthquake and Tsunami with 44,000 100-m Spaced Sensors (preprint, open access)
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