For the first time, the mysterious ‘hum’ generated by the Earth’s movement deep underwater captured. This record could help scientist understand the inner workings of the planet and can give a better overall picture of our planet.
A team of scientists, in the late 1990s, found that at low frequencies Earth constantly vibrates even in the absence of earthquakes. Although ıt cannot be felt by humans sensitive seismic instruments were able to detect it.
For this continuous vibration, researchers have come up with a flurry of explanations since the discovery, with possibilities ranging from ocean waves moving over the sea floor to atmospheric disturbances. But none of the theories was considered true because only by using seismometers on land the vibration was detected.
Nobody knew exactly where these vibrations are coming from. if they captured the vibration at the sea floor Scientists would better quantify the source of it.
Now, thanks to seismic instruments, scientists were able to record the Earth’s vibrational “hum” on the bottom of the ocean. Researchers can use the findings to map the interior of Earth with more detail and accuracy and the recording could provide new insights into the source of the vibration.
But, what exactly lies behind the oscillations remains a mystery
Lead author of the study, a geophysicist at the Paris Institute of Earth Physics in Paris, Martha Deen said: “Earth is constantly in movement, and we wanted to observe these movements because the field could benefit from having more data.”
Researchers, upon xamining low-frequency seismic signals, discovered that 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.