17/01/2022
We could soon have a faster and more efficient tsunami early-warning system!
When earthquakes caused by tectonic or volcanic activity occur, they often release tremendous amounts of energy that create tsunamis. Usually, people in coastal areas can be warned about an impending tsunami through the recession of seawater in coastal areas or through an early-warning system.
Now, there could be a much faster way to detect tsunamis and warn people about its impending devastation.
In a recent study published in the American Geophysical Union’s Journal of Geophysical Research: Solid Earth, geophysicists Zhiheng Lin, Hiroaki Toh, and Takuto Minami showed evidence that tsunamis generate a magnetic field as they move conductive seawater across the Earth’s magnetic field. This idea has been previously theorized by scientists but never proven using data.
To finally prove this hypothesis, the three geophysicists from Kyoto University gathered data from underwater magnetic field sensors during two two major earthquakes that generated tsunamis — the 2009 Samoa Earthquake and the 2010 Chile Earthquake. The data showed that there were indeed changes in the magnetic field in the area approximately one minute before the tsunami arrived.
“Pressure sensors respond to the tsunami right after the tsunami sea level changes,” says Lin. “But the tsunami magnetic field arrives earlier than the tsunami sea level change.”
These findings could change the way data is gathered about impending tsunamis. Current tsunami early-warning systems often consist of devices called seafloor bottom pressure recording (BPR) packages, also known as tsunameters. These devices are placed on the ocean floor near coastal areas and detect water pressure changes caused by tsunamis.
Once a tsunami is detected, these devices then send the data they gathered to surface buoys floating on the ocean surface that are tethered to an anchor on the ocean floor. These buoys send the data to satellites orbiting in space that relay the data to a tsunami warning center such as the United States’ Pacific Tsunami Warning Center (PTWC). These tsunameters rely on the tsunami passing over the devices to detect it.
However, by deploying magnetometers in deeper parts of the ocean, a tsunami can be detected even before it passes by sensing changes in the water’s magnetic field. The data can then be used to warn coastal communities earlier than usual while the tsunami is still several kilometers away from shore, allowing more time for evacuation to higher ground.
This development could benefit tsunami-prone countries such as the Philippines, particularly by improving our current tsunami early-warning systems. In 2012, experts from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and Advance Science and Technology Institute (ASTI) — both agencies under the Department of Science and Technology (DOST) — installed the Community Tsunami Detection and Warning System off the coast of Pangasinan and Albay. The system uses an array of underwater tsunami ultrasonic sensors that detects changes in sea levels along coastal areas after an earthquake.
Sources:
Lin, Z., Toh, H., & Minami, T. (2021). “Direct comparison of the tsunami-generated magnetic field with sea level change for the 2009 Samoa and 2010 Chile tsunamis.” Journal of Geophysical Research: Solid Earth, 126, e2021JB022760. https://doi.org/10.1029/2021JB022760
Crane, Leah (December 24, 2021). “Tsunamis create magnetic fields that could act as early warning system.” New Scientist.
https://www.newscientist.com/article/2303153-tsunamis-create-magnetic-fields-that-could-act-as-early-warning-system/
Schultz, Isaac (December 23, 2021). “Magnetic Fields Could Be Early Warning That a Tsunami Is on the Way.” Gizmodo.
https://gizmodo.com/magnetic-fields-could-be-early-warning-that-a-tsunami-i-1848265914
De Leon, Angelica (November 28, 2012). DOST’s tsunami warning system makes coastal communities safer. Department of Science and Technology.
https://www.dost.gov.ph/knowledge-resources/news/35-2012-news/213-dost-s-tsunami-warning-system-makes-coastal-communities-safer.html
