Tsunamis are preceded by changes in magnetic fields

Tsunamis create magnetic fields as they move conductive water through the Earth’s ’s own magnetic fields. A new study from the American Geophysical Union shows that these changes in magnetic fields can be detected minutes before changes in sea level. 

The researchers hope these magnetic field changes will improve early detection of tsunamis. 

“The motion of conductive seawater by tsunamis can generate magnetic fields in the presence of the background geomagnetic main field,” explained the study authors.

“Previous studies found that, using the tsunami-generated seafloor magnetic field, it is possible to predict the propagation direction and wave height prior to the actual arrivals of tsunamis.”

The scientists used data from magnetic fields to predict the height of waves from two tsunamis. 

The predictive power of the magnetic field was tested on a 2009 tsunami in Samoa and a 2010 tsunami in Chile. The research found that in both cases, magnetic fields were detected before water level changes. 

The study also showed that water depths affect how much earlier the magnetic fields are detectable.

“It is very exciting because in previous studies we didn’t have the observation [of] sea level change,” said study senior author Zhiheng Lin, 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.”

Neesha Schnepf, a geomagnetics scientist at University of Colorado Boulder who wasn’t involved in the study, explained the importance of the research.

“They did something that basically needed to be done,” said Schnepf. “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.”

:I think the practical goal would be if your ability to model tsunamis is so improved, you could come up with much better predictions of what areas might need to be warned [and] how badly it might hit certain places.”

The study is published in the Journal of Geophysical Research: Solid Earth.

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By Zach Fitzner, Earth.com Staff Writer