Exhaustive seismic data from repeating earthquakes and new data-processing methods have yielded the best evidence yet that the Earth's inner core is rotating - revealing a better understanding of the hotly debated processes that control the planet's magnetic field.
The new study by researchers from the University of Illinois at Urbana-Champaign is published in the journal Earth and Planetary Science Letters.
A new study of Earth's inner core used seismic data from repeating earthquakes, called doublets, to find that refracted waves, blue, rather than reflected waves, purple, change over time -- providing the best evidence yet that Earth's inner core is rotating.
Credit: Graphic by Michael Vincent
Usage Restrictions: This graphic may be used in stories related to this press release. Credit is required.
Geologists do not fully understand how the Earth's magnetic field generator works, but suspect it is closely linked to dynamic processes near the inner core-outer core boundary area, the researchers said. Shifts in the location of the magnetic poles, changes in field strength and anomalous seismic data have prompted researchers to take a closer look.
"In 1996, a small but systematic change of seismic waves passing through the inner core was first detected by our group, which we interpreted as evidence for differential rotation of the inner core relative to the Earth's surface," said geology professor and study co-author Xiaodong Song, who is now at Peking University.
"However, some studies believe that what we interpret as movement is instead the result of seismic waves reflecting off an alternately enlarging and shrinking inner core boundary, like growing mountains and cutting canyons."
The researchers present seismic data from a range of geographic locations and repeating earthquakes, called doublets, that occur in the same spot over time.
"Having data from the same location but different times allows us to differentiate between seismic signals that change due to localized variation in relief from those that change due to movement and rotation," said Yi Yang, a graduate student and lead author of the study.
The team found that some of the earthquake-generated seismic waves penetrate through the iron body below the inner core boundary and change over time, which would not happen if the inner core were stationary, the researchers said.
"Importantly, we are seeing that these refracted waves change before the reflected waves bounce off the inner core boundary, implying that the changes are coming from inside the inner core," Song said.
The basis of the debate lies in the fact the prior studies looked at a relatively small pool of somewhat ambiguous data generated from a method that is highly dependent on accurate clock time, the researchers said.
"What makes our analysis different is our precise method for determining exactly when the changes in seismic signals occur and arrive at the various seismic stations across the globe," Yang said. "We use a seismic wave that did not reach inner core as a reference wave in our calculations, which eliminates a lot of the ambiguity."
This precise arrival time analysis, an extensive collection of the best quality data and careful statistical analysis performed by Yang, are what give this study its power, Song said. "This work confirms that the temporal changes come mostly, if not all, from the body of the inner core, and the idea that inner core surface changes are the sole source of the signal changes can now be ruled out," he said.
The National Science Foundation and the Natural Science Foundation of China supported this study.
To reach Xiaodong Song, call 217-714-5125; email email@example.com.
A hydrological model leads to advances in the creation of a world water map
06.05.2020 | University of Córdoba
Shrinking snowcaps fuel harmful algal blooms in Arabian sea
04.05.2020 | Earth Institute at Columbia University
TU Graz researcher Francesco Greco has developed ultra-light tattoo electrodes that are hardly noticeable on the skin and make long-term measurements of brain activity cheaper and easier.
In 2015 Francesco Greco, head of the Laboratory of Applied Materials for Printed and Soft electronics (LAMPSe, http://lampselab.com/) at the Institute of Solid...
Quantum Spin Liquids are candidates for potential use in future information technologies. So far, Quantum Spin Liquids have usually only been found in one or two dimensional magnetic systems only. Now an international team led by HZB scientists has investigated crystals of PbCuTe2O6 with neutron experiments at ISIS, NIST and ILL. They found spin liquid behaviour in 3D, due to a so called hyper hyperkagome lattice. The experimental data fit extremely well to theoretical simulations also done at HZB.
IT devices today are based on electronic processes in semiconductors. The next real breakthrough could be to exploit other quantum phenomena, for example...
Physicists at the Institute of Science and Technology Austria (IST Austria) have invented a new radar prototype that utilizes quantum entanglement as a method of object detection. This successful integration of quantum mechanics into our everyday devices could significantly impact the biomedical and security industries. The research is published in the journal Science Advances.
Quantum entanglement is a physical phenomenon where two particles remain inter-connected, sharing physical traits regardless of how far apart they are from one...
Scientists from the University of Groningen have developed a method that combines different resolution levels in a computer simulation of biological membranes.
ESF-funded project "SenseCare” at Chemnitz University of Technology successfully completed - Therapeutic support, especially for diabetes mellitus
In the medical field, flexible and highly sensitive sensors can combine diagnostics and treatment with high comfort for patients.
07.04.2020 | Event News
06.04.2020 | Event News
02.04.2020 | Event News
13.05.2020 | Medical Engineering
13.05.2020 | Life Sciences
13.05.2020 | Life Sciences