I have written in this column before about earthquakes, particularly how they impact the Pacific Northwest, and what you need to do to be prepared when one strikes. Forecasting the weather is difficult enough, but forecasting earthquakes is something all together different. Once an earthquake strikes getting the word out quickly is of vital importance. That means the sooner one is detected the sooner people can be alerted.
There are seismometers positioned around the world that react when there is a quake and they measure the intensity. What if we could have even more sensors that would react to these temblors? Believe it or not we actually do, but nobody knew until now.
Seismologists at the California Institute of Technology (Caltech) in conjunction with Google optics experts have devised a method to use existing underwater communication cables to detect earthquakes. Communications companies began laying the network of cables back in the 1980sThe hope is that their research will provide improved earthquake and tsunami warning systems worldwide. There are over 62 million miles of underwater communication cables worldwide lying on the ocean floor that can be used for this very important purpose.
According to the scientists utilizing the undersea cables would be much more cost effective than producing and positioning many more seismometers around the world. They will be analyzing the light that travels through “lit” fibers in existing and functioning submarine cables. From an article published February 26, 2021 in phys.org titled “Using deep-sea fiber optic cables to detect earthquakes” written by Kinn Fesenmaier (Caltech) comes the following quote. According to Zhongwen Zahn, Ph.D., Assistant Professor of geophysics at Caltech “This new technique can really convert the majority of submarine cables into geophysical sensors that are thousands of kilometers long to detect earthquakes and possibly tsunamis in the future. We believe this is the first solution for monitoring seismisity on the ocean floor that could be feasibly implemented around the world. It could complement the existing network of ground-based seismometers and tsunami-monitoring buoys to make the detection of submarine earthquakes and tsunamis much faster in many cases.
The cable these scientists used for their experiments is the fiber optic Curie Cable that runs for more than 6,000 miles between Los Angeles, California and Valparaiso, Chile. Submarine cables are better than surface fiber optic cables because there isn’t the change in polarization of light, and interference from lightning strikes, temperature changes, etc. at the bottom of the cold dark ocean bed. During their tests no tsunamis were detected, but they could measure the changes in polarization of the light by pressure changes made by ocean swells as they passed by the cable.
During the nine months of testing reported in the new study titled “Optical polarization-based seismic and water wave sensing on transoceanic cables” was published in Science. Discussing their results Dr. Zahn said “This means we can detect ocean waves, so it is plausible that one day we’ll be able to detect tsunami waves.”
Since we live in the Pacific Northwest being able to detect earthquakes and particularly tsunamis with better accuracy could be a huge lifesaver, particularly when they occur west of us across the Pacific Ocean.
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