Study shows magnetic fields can act as early warning signs for tsunamis
Every minute matters in the event of a tsunami, and over the years we have seen a number of interesting ideas around how these giant waves might be better predicted ahead of time. These include monitoring underwater sound waves triggered by earthquakes, and using submarine cables as giant seismic networks. Scientists are now throwing another possibility into the mix, showing how the magnetic fields generated by tsunamis can be detected before the massive, devastating waves make it to shore.
It was known that tsunamis generate magnetic fields as they cause massive shifts in conductive seawater, and previous research has indicated that this magnetic field takes shape ahead of the dramatic and dangerous changes in sea level. What has remained unclear was the distinct relationship between the two, with research lacking measurements of the magnetic field and associated sea level changes needed to demonstrate the precise connection.
By drawing on data from the 2009 tsunami in Samoa and 2010 tsunami in Chile, the authors of this new study claim to have connected the dots. This data provided the scientists with the necessary information to compare the magnetic fields generated by the tsunamis with the resulting changes in sea level, which indeed confirmed that the former took shape before the latter.
Further, the analysis showed that the magnitude of the magnetic field can be used to predict the height of the impending tsunami. How much earlier the magnetic field arrived depended on how deep the water was, but at a depth of 4,800 meters (15,800 ft), the scientists found it arrived around a minute ahead of the changes in sea level.
“It is very exciting because in previous studies we didn’t have the observation [of] sea level change,” says Zhiheng Lin, senior study author and a geophysicist at Kyoto University. “We have observations [of] sea level change, and we find that the observation agrees with our magnetic data as well as theoretical simulation.”
The scientists say the study provides the basis for improved modeling systems for tsunamis, which can help predict the arrival time, height and locations of the devastating waves and assist with disaster preparedness. They also note that the technique would only be useful in deep-sea rather than coastal environments, where the deeper waters help filter out environmental noise and allow for clear detection of the tsunami signal.
“They did something that basically needed to be done,” says Neesha Schnepf, a researcher of geomagnetics at the University of Colorado, Boulder who was not involved in the study. “We’ve needed a study that compared the magnetic field data with the sea level change from the pressure data, and I’m pretty sure they’re the first to really compare how well the sea level from magnetic field matches the sea level from pressure, so that’s definitely very useful.”
The research was published in the journal JGR Solid Earth.
Source: American Geophysical Union
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