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Google is testing its earthquake and tsunami warning system with existing network of undersea fiber optic cables to detect disturbances on the seafloor.
These cables are used to carry data, and internet, across continents. During transmission, light’s state of polarization (SOP) changes when it encounters mechanical disturbance along the cable. Seismic activity can be detected by tracking these disturbances, Google said in blog post.
The technique works across tens of thousands of kilometres and relies on equipment already present in the existing fiber optic system, where data travels as pulses of light at over two lakh kilometres per second, it added.
In October 2019, Google started performing spectral analysis of Stokes parameters to look at frequencies that are typical of earthquakes. The Stokes parameters measure the optical signal and help in identifying the disturbances in it.
About two months later, it detected a magnitude 7.7 earthquake away from Jamaica—1,500 km away from the closest point of one of its cables, the company said.
In subsequent months, it has detected earthquakes on the East Pacific Rise, a magnitude 6.1 earthquake, and off the shore near Valparaiso, Chile, a magnitude 4.5 earthquake.
After analysing the earthquake detection data, Dr. Zhongwen Zhan of the California Institute of Technology Seismological Laboratory showed that the technique can also help predict tsunami by detecting pressure changes in the ocean, Google said.
“When a cable runs near the earthquake epicentre, a tsunami warning system that transmits data at the speed of light could communicate a warning to potentially affected communities in milliseconds,” Google added.
Google’s earthquake detection approach involves understanding of complex seismic data with the help of scientists as different earthquakes produce different waveforms with several variables such as magnitude, location, and so on. Further, its technique is said to complement existing array of dedicated seismic sensors, and not replace them.