Fiber optic cables could revolutionize earthquake detection and monitoring

Many of the world’s largest and most devastating earthquakes strike beneath the ocean, where the lack of sensors makes quick warnings difficult. Most monitoring stations are on land.

“If we have a big earthquake under the water, like that Kamchatka earthquake [this summer], our sensors that tell us an earthquake just happened are really quite far away,” said Emily Brodsky, a geophysicist at UC Santa Cruz. “And so we’re sort of looking through this very fuzzy pair of glasses at the earthquake and making our best guess on what it’s gonna mean in terms of tsunamis or anything else.”

New research published Thursday suggests fiber optic cables on the ocean floor could serve as earthquake sensors, Brodsky said. She co-authored a commentary accompanying the paper.

With 70% of the planet covered by water, using telecommunications infrastructure as seismometers could fill major blind spots in earthquake detection in a relatively affordable and scientifically robust way.

While this is not the first paper describing the technique, it pushes the technology to new limits, focusing on how faults rupture underwater. That’s important because researchers could see that the fault was rupturing super fast, casting new light on the physics of earthquakes.

To use fiber optic cables this way, researchers partner with a company running the cables — in this case, Vero Fiber Networks — and attach a box containing a laser and a computer. The laser sends pulses into the fiber that echo all along its length.

If the cable stretches due to earthquake movements, the light echoes change. The changes can be converted into measurements, giving a fine-grained view of the event. Even in California, which is relatively well-covered by seismometers, stations are spaced several miles apart. Fiber optic sensing allows measurements down to the scale of feet.

With this higher resolution, earthquake early warning alerts, like Californians receive through MyShake, could improve.

“Traditionally, it’s very, very hard to see for big earthquakes, how long is the fault that’s rupturing, in what direction is it going?” said James Atterholt, a seismologist with the U.S. Geological Survey and author on the research paper. “And this technology shows that with modifications, with advancements, that this could be done in real time.”

Some experts are skeptical that predicting earthquakes is possible. Others, including Brodsky, are cautiously optimistic.

“Just to be clear, no, we do not know how to predict earthquakes. But we do want to study whether or not they’re predictable,” she said. “We are in a totally different place than we were 15 years ago.”

Scientists now have better hypotheses for how prediction could work, Brodsky said, but “to a large extent, we’re instrumentally limited and we need the investment. And it’s kind of that simple.”