GPS signals can detect tsunamis better and faster than seismic sensors

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GPS networks are already an important part of everyday life around the world, but an international team of scientists have found a new, potentially life-saving use for them: tsunami warnings.

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Researchers at University College London and universities in Japan studied the GPS network’s ability to detect tsunamis and concluded that the instruments can indeed detect destructive waves from space. They also determined that GPS could provide more detailed information than current detection systems at an extremely low cost, allowing authorities to issue more accurate warnings before a tsunami hits a shore.

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Tsunamis are formed when ocean waters are abruptly displaced by earthquakes, landslides, or volcanic eruptions. In the deep ocean, the waves are usually less than a foot high, but as they approach land at speeds up to 500 miles per hour, they quickly rise in height before flooding the coastline. GPS networks can detect these waves long before they hit the ground.

Although the disturbance on the surface of the ocean is small, it is enough to create a ripple effect in the atmosphere. As the air is pushed up, the acoustic wave travels all the way to the ionosphere, about 186 miles above the Earth, getting stronger as it travels. There, the density of electrons in the ionosphere is reduced by a wave, which directly affects the radio signals sent from GPS satellites to ground receivers. Researchers have developed a way to interpret changes in radio signals to gather important information about a tsunami.

Animation of particles disturbing the ionosphere over a tsunami.

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Image credits: University College London

Currently, tsunami warnings are issued based on seismic activity. The warnings are not necessarily very precise, they only indicate that a tsunami may occur at some point in the near future, but provide little other detail.

“In 2011, Japan’s warning system underestimated [Tōhoku] wave height. A better warning would probably have saved lives and reduced widespread destruction by allowing people to move to higher ground and away from the sea,” said Professor Serge Guillas of UCL Statistical Science and the Alan Turing Institute and senior author on the paper. Press release. “Our study, a collaborative effort between statisticians and space scientists, demonstrates a new tsunami detection method that is inexpensive because it relies on existing GPS networks and can be implemented worldwide, complementing other tsunami detection methods and improving accuracy. warning systems.”

The researchers suspect that if GPS data had been used during the Tohoku disaster, an accurate tsunami warning could have been issued at least 10 minutes before the wave hit land, potentially giving more people time to prepare for an impact.

The team believes that with further research, they will be able to more accurately determine the size and shape of a tsunami based on GPS radio signals.

“Based on my experience of working for the Japanese government in the past and observing the damage caused by the tsunami, I believe that if this study is implemented, it will undoubtedly contribute to saving lives,” said the Ph.D. researcher Ryuichi Kanai of UCL Statistical Science and the Alan Turing Institute, co-author of the paper.

Researchers’ the study was published in the journal Natural Hazards and Earth System Sciences last month.

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