Rebound earthquakes, as they “bounce” off the core, are already revealing new details about the structure of this core, according to study Posted on February 21 in Nature Communications. More specifically, it betrays more and more the existence of a second layer at the heart of the so-called inner core: it is a thing was suspected Twenty years, but not easy “map.”
The difficulty is not in having instruments sensitive enough to detect such distant oscillations. These are echoes of an earthquake occurring at a point on the planet Bounce to another point, opposite the planetand return to the starting point by crossing the central part, on a round trip that can last for hours: a single “crossing” from one point on Earth to its opposite is estimated to be about 20 minutes.
The researchers first had to work out the echoes of 600 major earthquakes in the past decade, and Compare how quickly their waves weaken Crossing the core, but also to characterize the impact that takes place, on this weak, inner core – the solid and metallic part, estimated to have a radius of 1220 km. Once there, Try to spot the differences, if anywithin the inner core itself.
Hence one of the conclusions of the Australian seismologists in this new study is that the hypothesis of the central layer, distinct from the rest of the inner core, is strengthened, and that its “transition” to the upper layer could be a “fossilization of a cosmic layer”. that occurred hundreds of millions of years ago, or even longer.
If they’re right, we should go through the textbooks, and describe our planet in five layers: Earth’s crust, mantle, outer core, inner core, and now the central part of the inner core.
Image: Argonne National Laboratory/ Flickr / CC 2.0
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