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Although oceans cover 70 percent of Earth's surface, there are surprisingly few underwater earthquake sensors. While seismic activity frequently occurs in the open ocean, most detection devices are situated on land, with some offshore sensor initiatives in places like Japan, the U.S., and Canada.
To enhance earthquake monitoring for tremors and quakes occurring far from existing sensors, researchers from the UK, Italy, and Malta have proposed using the internet. According to Science News, fiber-optic cables already in place for global communications could be repurposed as seismic sensors through the use of lasers.
A recent study published in Science suggests sending a laser beam through an optical fiber and analyzing how the light is altered. If the cable experiences seismic vibrations, the light passing through it will change accordingly.
The method, which was tested during earthquakes in Italy, New Zealand, Japan, and Mexico, could enable scientists to utilize data from various undersea cables to detect and analyze earthquake activity. This includes identifying the epicenter and estimating the magnitude. For example, quakes in New Zealand and Japan were detected from a fiber-optic cable located in England, while an earthquake in the Malta Sea was measured from an undersea cable between Malta and Sicily, more than 50 miles from the epicenter.
Marra et al., Science (2018)While seismic sensors placed on the ocean floor are costly, their value in saving lives is undeniable. For instance, during the catastrophic 2011 Japanese earthquake, the country’s extensive early-warning system, including underwater sensors, provided a 90-second warning to Tokyo residents before the shaking started.
By using the existing cable networks that stretch across the ocean floor, scientists could gather data on earthquakes that originate in the ocean and are too faint to be picked up by land-based seismic sensors. Since hundreds of thousands of miles of these cables already span the globe, this approach is far more affordable than installing new sensors on the ocean floor, offering scientists potential access to global earthquake data, rather than just from regions with offshore sensors.
Although the researchers have yet to test the laser technique on the long fiber-optic cables between continents, it is not yet ready for large-scale use. However, it holds potential to enhance tsunami detection, monitor earthquakes in remote locations like the Arctic, and more in the future.
