We may be able to predict deadly tsunamis using their magnetic fields. When large amounts of seawater move at once, they generate a small magnetic field. This magnetic field can be used to predict tsunamis before the sea level changes at the shore.
Researchers at Kyoto University in Japan, led by Zhiheng Lin, have used data from two tsunamis that occurred in Samoa in 2009 and Chile in 2010 to demonstrate the feasibility of this approach. They found that the changes in the magnetic field accurately corresponded to the sea level changes caused by the tsunamis.
Traditionally, pressure gauges placed on the sea floor are used to detect the movement of a tsunami. However, these gauges only detect the tsunami after it has already passed over them. Lin and his team took a different approach by using a set of sensors in the south Pacific Ocean to measure the magnetic field and sea level changes simultaneously during the two tsunamis. They discovered that the tsunamis were preceded by changes in the magnetic field.
The magnetic field changes were observed to arrive about one minute earlier than the sea level changes. The exact timing may depend on the water’s depth, according to Lin. This is particularly significant because pressure sensors are typically located too close to coastlines to provide timely warning of a tsunami.
Magnetometers, which measure magnetic fields, could be strategically placed in the middle of the open ocean’s abyssal plain, far away from coastlines. This would allow for early detection and provide data on tsunamis before they reach the pressure buoys near the coastlines.
By combining the early warning provided by the magnetic field changes with the ability to predict the height of tsunami waves, coastal communities can better prepare for incoming tsunamis.
