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Investigating the Earth’s Mantle Using Microseisms


An ocean wave prepares to break, while other waves close in behind it under a hazy sky.

The source is Geophysical Research Letters.

The ocean is always bustling with movement. The consistent churning and rising creates microseisms, which are small vibrations of the Earth that can also be triggered by human actions such as cars driving.

Microseisms emit significantly lower amounts of energy compared to earthquakes, yet they remain valuable sources of data for scientists. Unlike the sudden and isolated jolt of an earthquake, microseisms occur continuously, creating a consistent underlying noise that can reveal details about the inner structure of the Earth that cannot be obtained from studying larger seismic occurrences.

In recent study, Kato and Nishida investigate microseisms generated by oceanic ambient noise, which can propagate as body waves through the Earth’s mantle. Similar to larger seismic waves, these microseisms can also travel along the Earth’s surface as surface waves or within its interior.

The scientists studied information gathered from 690 seismic monitoring stations, which detected 5,780 small tremors in the North Atlantic Ocean and both the North and South Pacific. Rather than using seismic interferometry, a common method for studying seismic activity by assuming that tremors occur everywhere, the researchers treated these microseisms more similar to larger earthquakes. They used a new receiver function method and viewed the microseismic body waves as originating from separate sources in order to create a 3D image of the Earth’s mantle structure.

The images confirmed the depths of the changes in rock density and composition, known as mantle discontinuities, which occur at 410 and 660 kilometers beneath the Earth’s surface. The researchers suggest that their novel method for interpreting microseismic body waves may provide a deeper understanding and potential for further exploration of the mysterious inner structure of our planet. (Geophysical Research Letters, https://doi.org/10.1029/2023GL105017, 2023)

“I am a science writer, Rebecca Owen (@beccapox)”

Reference: Owen, R. (2023). Investigating the Earth’s mantle using microseisms. Eos, 104. Retrieved from https://doi.org/10.1029/2023EO230355 on September 21, 2023.

Text © 2023. AGU. CC BY-NC-ND 3.0

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