CT for the Earth in the Ocean

Date:Nov 16, 2022    |  【 A  A  A 】

(Text by DONG

Dongdong was deploying the hydrophone streamer. Credit: Institute of Oceanology, Chinese Academy of Sciences

The Earth we live on is infinitely spectacular. Plateaus, mountains, rivers, grasslands and valleys all bring us the enjoyment of beauty. However, most of what we see is on land. When it comes to the ocean, covering about 71 percent of the Earth's surface, is there anything magnificent beneath the thick layer of seawater? If so, how did they form?

As a marine geophysicist, I use geophysical methods to explain the features of the seafloor. In fact, scientists have been working for decades to reveal a wealth of seafloor features. Acoustic detection method plays an important role in the marine exploration.

In this photo, I am deploying the hydrophone streamer, main part of the marine multichannel seismic system, on the R/V Science of the Institute of Oceanology of the Chinese Academy of Sciences. The streamer is towed behind the ship, like a 3-km-long "tail". The "tail" is fitted with hundreds of sensors that receive acoustic signals from seismic waves generated by the bursting of bubbles triggered by air guns in the water. The waves travel down the water column and through the seafloor, where they are reflected back to the sea surface and received by the streamer. The acoustic signals are then processed in the laboratory to produce a profile that reflects the relief of seafloor and the structure below.

Using the seismic profiles, we can identify oil and gas in the strata, and even investigate magma flow in the Earth's crust. Based on a large number of seismic profiles, combined with numerical modeling and geochemical analysis of the sampled rocks, we can further explain how these geological structures formed.

So, as you can see, what we're doing is a lot like medical CT, except we're doing CT for the Earth instead of the brain. But fear nothing, guys, our Earth is not sick, and we just want to figure out how it works.

(Editor: ZHANG Yiyi)

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