Scientists have already figured out ways to harness these cables in order to detect Earthquakes on land, but doing so tends to require the use of spare “Dark Fibre” cables and or special kit, which can be expensive and isn’t particularly viable for existing subsea links. Equally, the high cost of installing Earthquake seismometers on the sea floor means that there’s an ocean sized gap in monitoring that needs to be filled.
Suffice to say that scientists have been trying to figure out a new and more cost-effective way of solving this problem, which is exactly what they seem to have done. But first it’s important to understand that optical fibre infrastructure typically transmit data using pulses of laser light.
The solution that researchers at the California Institute of Technology (Caltech) came up with involves monitoring those light pulses in a live cable, specifically the polarization (i.e. its electric field oscillates in just one direction rather than any which way).
Various external events can change the polarization of light in a land-based fibre, such as lightning strikes and changes in temperature, but it’s a different story in the deep ocean, where the temperature remains fairly stable and there are few disturbances. As such the polarization is fairly stable, except for when there’s a big event like say.. an Earthquake or storm (large waves, tsunamis etc.).
The 9-month-long experiment – running between December 2019 and September 2020 – was able to successfully detect a total of 20 moderate-to-large quakes along the cable, including a 7.7 magnitude event off Jamaica that occurred on 28th January 2020 (this is notable because the Caribbean sits on the opposite side of America from the Curie cable).
By deploying this across more cables Seismologists could build up a much more detailed picture of such events, which may in turn result in earlier warnings and that could save lives. No tsunamis occurred during the monitoring period, but the cable did detect storm related changes in ocean swells (large waves etc.) and so it’s feasible that tsunamis could also be detected.
The team are now developing a machine learning algorithm that could help to detect such events and separate them out from other disturbances, such as sea life or ships moving the cable. This sort of approach will of course be much more effective when multiple fibres can be harnessed together to help root out such disturbances.