Stanford Shows How Fiber Optics Might Enable Global Quake-Warning Network

Rodiano Bonacci
Ottobre 23, 2017

Researchers at Stanford's School of Earth, Energy and Environmental Sciences have successfully tested a mechanism which shall use fibre optic network to monitor seismic events. Biondo Biondi, a professor at the aforementioned department at Standford has spent the previous year recording seismic events with the help of the three mile loop of fibre optic network spread underneath the Stanford University campus.

Thousands of miles of buried optical fibers crisscross California's San Francisco Bay Area delivering high-speed internet and HD video to homes and businesses. In case of DAS on fibre optic cables, the light passes through the fibre and the backscatter from various impurities in the glass is observed continuously. "Every meter of optical fiber in our network acts like a sensor and costs less than a dollar to install". If any physical force such as strain from any seismic activity stretches the cable then the backscatter changes and these changes can be logged in the system. Using fiber-based detections isn't something that's completely new, but it has previously been used for acoustic sensing that needed them wrapped in cement, or sticking them to a surface so that you ensured contact was made to the ground.

Since optical fibers work by bouncing light signals down a glassy cable, minor disturbances to that signal can be measured as they come back.

"People didn't believe this would work", Martin said.

This fiber optic seismic observatory, as they called it, was sacked up in September 2016, and it was able to record more than 800 events in its first year of operation. "This demonstrates that fiber optic seismic observatory can correctly distinguish between different magnitude quakes". This observatory can also serve as an natural disaster warning system because it can distinguish between P and S waves. P waves are particularly important to detect as they arrive before S waves and are typically the first waves felt from a seismic event. "One of our goals is to contribute to an early natural disaster warning system".

Geophysics professor Biondo Biondi repurposed some of those cables, along with an existing underground network of sensors, to create a virtual three-mile-long, figure-eight-shape subterranean seismometer.

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