An international team of researchers based from London to Japan is paving the way for faster and far more accurate detection parameters surrounding tsunamis. Conventional methods rely heavily on seismic sensors, but the group vies to bridge a less costly and more streamlined approach to the form through long-existing sophisticated GPS networks.
Their work was published in full via the Natural Hazards and Earth Systems Sciences journal nearly a month ago, highlighting their efforts specifically regarding a 2011 earthquake in Tohoku-Oki. The team's research consists of various GPS data, leveraging this information to identify alterations to radio signals affected by a wave that's reducing the electron density in the Earth's ionosphere.
A tsunami typically forms due to an earthquake occurring beneath the sea, as well as nearby volcanic eruptions or even landslides. Ocean water gets picked up in droves, starting first in deep ocean areas where the waves reach no more than about a foot in height. Upon reaching coastal land masses, said waves are now reaching incredible heights at speeds of up to nearly 500 miles per hour, which is a testament to the necessity of far faster data streams in relation to said natural disasters.
The question then is how this assorted international team figured out a way to detect such terrifying forces of nature at the average GPS satellite altitude of 12,550 miles from the Earth's surface. Utilizing the GPS satellite's radio signals, the team detected slight disturbances amid the ocean's surface. As mentioned previously, the Earth's ionosphere is key to the whole process.
Following a massive disturbance beneath the ocean, air drives skyward from the main point of commotion, followed by an acoustic wave, all of which ascends to the 186 mile-high ionosphere. Amid this journey, the wave grows in scale, blasting into the ionosphere, where GPS satellites can then detect the aforementioned reduced electron density caused by the initial wave.
These satellites work in tandem with ground receivers, sending back and forth a radio wave that acts as the buffer. Any major calamity can theoretically be charted at the point of its very birth or as close to it as is scientifically possible. In their report, the international team of researchers posited that in the case of the Tōhoku tsunami disaster, GPS data readings may well have been able to spot the calamity and alerted authorities at least 10 minutes prior to the wave reaching landfall.
"In 2011, Japan's warning system underestimated the [Tōhoku] wave's height," explains senior author of the report, Professor Serge Guillas, in a press release. "A better warning may have saved lives and reduced the widespread destruction that occurred, allowing people to get to higher ground and further away from the sea."
Contemporary methods with seismic sensors tend to offer little in the way of accurate and full-fledged details surrounding a tsunami or general disaster of the ilk. In most cases, seismic readings merely offer a potential when as opposed to where it started, how tall it may be, and how much time remains before inevitable impact.
Adds Guillas, "Our study, a joint effort by statisticians and space scientists, demonstrates a new method of detecting tsunamis that is low-cost, as it relies on existing GPS networks, and could be implemented worldwide, complementing other ways of detecting tsunamis and improving the accuracy of warning systems."
Although the science isn't there just yet, as some time still remains before the team can more accurately determine a tsunami's precise shape and size, the initial data proves incredibly worthwhile and is beneficial for the future.
