Changes in GPS signal can be a more effective method to warn of tsunamis

A new method to detect tsunami using the satellites gps that orbit the Earth could serve as an effective warning system for countries around the world. This is the conclusion of a study led by researchers from UCL (University College London) and also made up of universities in Japan.

The study, which was published in the journal Natural Hazards and Earth System Sciences, states that, although the initial waves of a tsunami are usually a few centimeters high, they cause a disturbance in the atmosphere by pushing air up and creating an acoustic wave that amplifies as it rises.

This movement generates a reduction in the density of electrons in the ionosphere (300 km above the surface of the Earth) that affects radio signals sent by satellites gps to receivers gps on land. This can slow down or speed up different parts of the signal, or change the direction of the signal, depending on the frequency.

For the study, a new way of detecting this drop in electron density of altered GPS signals was developed.

Looking at GPS data during the 2011 Tohoku-Oki earthquake and tsunami, researchers found that a tsunami warning could have been issued with confidence within 15 minutes of the occurrence of the tsunami. earthquakethat is, at least 10 minutes before the first tsunami that reached the east coast of Japan.

They also found that a warning could have been issued using data from only 5% of the 1,200 recipients gps from Japanwhich means that the method could be used in countries with a sparser GPS network than Japan.

Advantages over other techniques

Many existing tsunami warning systems infer tsunami waves from earthquakes, but this new method could be used to predict incoming tsunamis with sources other than earthquakes, such as landslides and volcanic eruptions.

Furthermore, the method could also be used to predict second or third waveswhich helps determine whether a tsunami warning should be canceled or maintained after the first wave.

In a statement, Professor Serge Guillas (UCL Statistical Science and the Alan Turing Institute), lead author of the paper, noted that current warning systems tsunami cannot accurately predict height of a tsunami wave.

He recalled that, in 2011, Japan’s warning system underestimated the height of the wave and better warning could have saved lives, allowing people to reach higher ground and further from the sea.

“Our study, a joint effort of statisticians and space scientists, demonstrates a new method of detecting tsunami which is low cost, since it is based on networks gps existing and could be implemented worldwide, complementing other ways of detecting tsunami and improving the accuracy of warning systems”assured.

Tsunami waves are low in deep water, but can travel at jet speed (up to 800 km per hour in deep water) and, as they enter shallower water, they slow down and increase in height.