Scientists Capture Mysterious Hum On Ocean Floor

Posted: Dec 9 2017, 2:39pm CST | by , in News | Latest Science News

Scientists Capture Mysterious Hum on Ocean Floor
Credit: NASA

The vibration detected from seismometers on the ocean sea floor can give a better overall picture of our planet

In the late 1990s, a team of researchers discovered that Earth constantly vibrates at low frequencies even in the absence of earthquakes. The vibration is so faint it cannot be felt by humans. However, sensitive seismic instruments were able to pick it up.

In the years since the discovery, scientists have come up with a flurry of explanations for this continuous vibration, with possibilities ranging from atmospheric disturbances to ocean waves moving over the sea floor. But none was considered conclusive. This is likely because the vibration was only detected by using seismometers on land. Scientists would better quantify the source of this vibration if they captured it at the sea floor.

Now, using seismic instruments, researchers were able to capture the Earth's vibrational "hum" on the bottom of the ocean. Not only does the recording could provide new insights into the source of the vibration but it could also be used to map the interior of Earth with more detail and accuracy.

"Earth is constantly in movement, and we wanted to observe these movements because the field could benefit from having more data.” Martha Deen, a geophysicist at the Paris Institute of Earth Physics in Paris and lead author of the study said.

When researchers examined low-frequency seismic signals captured by seismic instruments, they found that they were persistent and cannot be confused with the shaking of earthquake.

Capturing the hum at the ocean bottom is critical because ocean waves and seafloor currents generate high amounts of ambient noise. Moreover, 70 percent of the Earth's surface is covered by water, so being able to measure the hum on the sea floor would enable scientists to analyze data at global scale.

“Fairly early on, people realized this was caused by ocean waves. As instruments have gotten better, we've realized the hum's going on all the time." Spahr Webb of Columbia University's Earth Institute, who was not involved in the study, told National Geographic.

For the latest study, researchers first gathered seismic data from 57 seismometer stations located at the bottom of the Indian Ocean east of Madagascar. These stations were deployed from 2012 to 2013 as part of another earlier study. Then, they narrow it down to two stations with the highest data quality. After eliminating all the ambient signals like ocean infragravity waves and currents, the scientists compared the remaining data with the hum recorded from a land station in Algeria. They found that the observations were consistent. Together, they could help yield a more detailed picture of our planet's structure.

"That can be used to map the structure of the Earth," said Webb. "Getting data from new places is going to help."

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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