Scientists are always finding new things but this is quite interesting for a lot of different reasons. In recent times a study has been published that goes over findings from researchers at the University of Maryland.

By looking at seismic echos from hundreds of different earthquakes it seems there could be some kind of widespread structure near our planet’s core/mantle boundary. While more research will need to be done on this, it does mean there could be something hidden beneath the surface of our planet that we are not quite as aware of as we may have thought we were. At the moment we do not know what the composition of these structures are but in time we may figure things out. 

Science Daily wrote as follows on these findings:

The new research provides the first comprehensive view of the core-mantle boundary over a wide area with such detailed resolution. The study was published in the June 12, 2020, issue of the journal Science.

The researchers focused on echoes of seismic waves traveling beneath the Pacific Ocean basin. Their analysis revealed a previously unknown structure beneath the volcanic Marquesas Islands in the South Pacific and showed that the structure beneath the Hawaiian Islands is much larger than previously known.

“By looking at thousands of core-mantle boundary echoes at once, instead of focusing on a few at a time, as is usually done, we have gotten a totally new perspective,” said Doyeon Kim, a postdoctoral fellow in the UMD Department of Geology and the lead author of the paper. “This is showing us that the core-mantle boundary region has lots of structures that can produce these echoes, and that was something we didn’t realize before because we only had a narrow view.”

Earthquakes generate seismic waves below Earth’s surface that travel thousands of miles. When the waves encounter changes in rock density, temperature or composition, they change speed, bend or scatter, producing echoes that can be detected. Echoes from nearby structures arrive more quickly, while those from larger structures are louder. By measuring the travel time and amplitude of these echoes as they arrive at seismometers in different locations, scientists can develop models of the physical properties of rock hidden below the surface. This process is similar to the way bats echolocate to map their environment.

For this study, Kim and his colleagues looked for echoes generated by a specific type of wave, called a shear wave, as it travels along the core-mantle boundary. In a recording from a single earthquake, known as a seismogram, echoes from diffracted shear waves can be hard to distinguish from random noise. But looking at many seismograms from many earthquakes at once can reveal similarities and patterns that identify the echoes hidden in the data.

Using a machine learning algorithm called Sequencer, the researchers analyzed 7,000 seismograms from hundreds of earthquakes of 6.5 magnitude and greater occurring around the Pacific Ocean basin from 1990 to 2018. Sequencer was developed by the new study’s co-authors from Johns Hopkins University and Tel Aviv University to find patterns in radiation from distant stars and galaxies. When applied to seismograms from earthquakes, the algorithm discovered a large number of shear wave echoes.

“Machine learning in earth science is growing rapidly and a method like Sequencer allows us to be able to systematically detect seismic echoes and get new insights into the structures at the base of the mantle, which have remained largely enigmatic,” Kim said.

These researchers were able to find there is some kind of quite big patch of dense hot material beneath Hawaii and it could end up being much larger than expected. That all having been said, there still needs to be more research done on the matter before we really are capable of truly diving into things.

The abstract of the study published on these findings goes as follows:

 Scattering of seismic waves can reveal subsurface structures but usually in a piecemeal way focused on specific target areas. We used a manifold learning algorithm called “the Sequencer” to simultaneously analyze thousands of seismograms of waves diffracting along the core-mantle boundary and obtain a panoptic view of scattering across the Pacific region. In nearly half of the diffracting waveforms, we detected seismic waves scattered by three-dimensional structures near the core-mantle boundary. The prevalence of these scattered arrivals shows that the region hosts pervasive lateral heterogeneity. Our analysis revealed loud signals due to a plume root beneath Hawaii and a previously unrecognized ultralow-velocity zone beneath the Marquesas Islands. These observations illustrate how approaches flexible enough to detect robust patterns with little to no user supervision can reveal distinctive insights into the deep Earth.

What do you think this could be? I for one am quite blown away and cannot wait to learn more. I guess it really does show now more than ever that as time progresses and technology becomes more advanced we’re going to be learning things about our planet that we otherwise would have never picked up on. 

Leave a Reply