JOIN USGoogle bets on submarine optic fibres to track earthquake, tsunami faster
For long, seismologists have tracked earthquakes and tsunamis by leasing undersea optic fibres (with sensors) from commercial operators. But, the range is limited to 100 km and some times the accuracy is much to be desired. Now, Google says it has developed new techniques that expand the range to thousands of km into the ocean.
The internet data, which is carried in the form of pulses of light inside the undersea optic fibres travel with speed up to 2,04,190 km per second. The optic cables are not always straight and bend at certain junctures between continents and this causes distortion of light. When the pulses of light meet at the end of the cable, the distortion is corrected by digital signal processing technique.
"One of the properties of light that is tracked as part of the optical transmission is the state of polarization (SOP). The SOP changes in response to mechanical disturbances along the cable and tracking these disturbances enables us to detect seismic activity," Google report said.
Based on the SOP data, Google first initiated a project on seismic tracking on terrestrial cables in 2013, but the environmental challenges caused too much disruption and, it was shelved.
After five years, scientists came with a new research paper claiming success in seismic tracking on both terrestrial and undersea conditions using the narrowband ultrastable laser. But, they tested it under 535 km for terrestrial and 96 km for subsea.
Google read the study and in October 2019, decided to conduct a similar experiment and go further deep into the sea. The Google experts tried to detect earthquakes based on spectral signatures—performing a spectral analysis of Stokes parameters to look at frequencies that are typical of earthquakes.
It began monitoring SOP on most of its undersea cable and found it to be stable, even after the signal traveling close to 10,500 km. However, on January 20, earlier this year, Google detected a major earthquake of magnitude 7.7(on Richter scale) of the Jamaica coast, 1,500km from one of Google's cable. It was able to detect in just five minutes of occurrence of the earthquake and recorded that the duration of the spike in seismic activity was around 10 minutes.
"We shared our results with Dr. Zhongwen Zhan of the California Institute of Technology Seismological Laboratory, who confirmed our observations and provided additional insight into travel times of different types of seismic waves and the expected frequency ranges of SOP excursions," Google report said.
Google recorded multiple seismic activities with mid-range earthquakes and a 6.1 magnitude in East Pacific, about 2,000 km from the optic cable. There was clear SOP activity with timing consistent with observations made in the Seismic tracking station in Tlapa, Mexico.
"We’re excited by the early success of detecting seismic events with subsea cables, which can improve our ability to observe both the Earth’s structure and earthquake dynamics. But this is just the beginning," Google said.
However, the company says its seismic tracking technique is still a work in progress model and more can be done to improve the accuracy and also early detection. These factors are very critical in sending a warning to the nearby coasts to save the lives of the people.
Google hopes to create a robust earthquake monitoring system. It says researchers need advanced mathematics and data analytics. For this, there is need a for advanced computing systems, the company says machine learning technology-based Google Cloud will play a critical role. It will come handy in analysing large data sets, which are some time beyond the ability of the human brain.
"We see this approach not as a replacement of dedicated seismic sensors but as a source of complementary information to enable early warnings for earthquakes and tsunamis. We’re humbled and excited by the possibility of collaborating with the optical, subsea and seismic research communities to use all of our cable infrastructure for greater societal benefits," Google noted.
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