Monitoring seismic activity around the world is an important task, but it requires equipment placed close to the places to be observed, and it is not easy if they are located in the middle of the ocean.
However, human ingenuity has found the solution. New Berkeley research and a technique, distributed acoustic sensing, will make it possible to transform the network of existing undersea fiber optic cables into a network of seismographs. An unprecedented global vision of the tectonic movements of the Earth can be created.
We don't know the sea well
Seismologists currently get almost all of their data from instruments on Earth, meaning that most of our knowledge of seismic activity is limited to a third of the planet's surface. We don't even know where all the really dangerous spots are, as there have been no comprehensive studies or long-term monitoring of the ocean floor.
“There is a huge need for seabed seismology”, explains the lead author of the study Nathaniel Lindsey in a Berkeley press release.
“Any instrumentation placed in the ocean, even just within the first 50 kilometers of the coast, will be very useful.”
Why haven't we already positioned a worldwide seismograph network?
Some might wonder why we haven't created a “network” of sensors on the planet's surface to monitor seismic and volcanic activity super precisely. After all, that's what we did with satellites, reaching a very precise level of detail.
Well, it's easier to send satellites into space than it is to position, operate and access the precision instruments required for long-term seismic work underwater.
What if there were already tools out there just waiting for us to use them? This is the idea that Lindsey and his colleagues are pursuing with the use of undersea fiber optic cables.
These cables carry data over long distances, sometimes as part of the Internet backbones and sometimes as part of private networks. But one thing that everyone has in common is that they use light to do it. Light that is diffused and distorted if the cable moves or changes orientation.
Distributed acoustic detection
By carefully monitoring this “backscatter” phenomenon col distributed acoustic detection you can see exactly where the cable bends and to what extent (sometimes with a margin of error of a few nanometers).
Essentially, distributed acoustic sensing allows researchers to observe a cable to discover the source of seismic activity. And we will be able to do it with an extraordinary level of precision.
The research has been published today in the journal Science.
