On March 23rd, 2022, TIMEleSS student Federica Rochira, published a new paper in Geophysical Journal international: Mapping the edge of subducted slabs in the lower mantle beneath southern Asia.
In this work, Federica Rochira, Lina Schumacher, and Christine Thomas from the Westfälische Wilhelms-Universität, Münster, investigate the presence of seismic structures in the Earth’s mantle by searching for seismic signals, and in particular signals from the edges of subducted slabs. They rely on an original approach that uses was that travel off the great circle path direction and are reflected or scattered off structures in the lower mantle and focus on areas of current and past subduction beneath Eurasia by using events from Indonesia and Japan recorded at the broad-band stations in Germany, Morocco and Namibia. Applying seismic array techniques, they measure the direction and traveltime of the out-of-plane arrivals and backtrace them to their location of reflection/scattering.
The results of the work indicate that most of the backtraced reflectors are located beneath southern Asia and are found shallower than 1500 km depth. They correlate well with the edges of prominent high velocity anomalies in tomographic inversions beneath southern Asia, which have been interpreted as remnants of fossil slabs of the subduction of the Tethys Oceans. They also observe few reflectors deeper than 1600 km that are located away from subducting regions and their positions coincide with the eastern edge of the African low velocity anomaly.
These observations suggest that the presence of reflectors in the mid-lower mantle is not exclusively related to current or past subducting regions, but widespread throughout the mantle.
The full details are in the following publication: F. Rochira, L. Schumacher, C. Thomas, Mapping the edge of subducted slabs in the lower mantle beneath southern Asia, Geophysical Journal International, 230, 1239–1252 (2022) [doi: 10.1093/gji/ggac110]
TIMEleSS members met virtually in June 2021 for a virtual meeting on crust subduction. The meeting was led by Matthias Krug, PhD student at WWU Münster, and currently visiting the Université de Lille for 6 months.
The meeting was an occasion for Matthias to present his work and get feedback from the rest of the group.
New publication in the French edition of The Conversation!
The Conversation is a network of not-for-profit media outlets that publish news stories written by academics and researchers.
In this paper, TIMEleSS PI S. Merkel speaks about the Earth’s lowermost mantle, seismology, high pressure / high temperature mineral physics, and how phase transformations help us understanding deep Earth processes!
TIMEleSS members are in Münster!
TIMEleSS PI C. Thomas is hosting a seismology training for TIMEleSS students.
Participants include TIMEleSS students E. Ledoux, J. Gay, F. Rochira, M. Krug, and guests from WWU Münster Mineralogy and Seismology labs.
The training is the opportunity to move on to the next step in the TIMEleSS project: combining Mineral Physics and Seismology observations and try to say something about deep mantle processes!
First publication for the TIMEleSS team: Kinetics and detectability of the bridgmanite to post-perovskite transformation in the Earth’s D″ layer.
Bridgmanite is a magnesian-iron mineral ((Mg,Fe)SiO3) with a crystal structure that is not stable under ambient conditions. It forms about 660 kilometers below the surface of the Earth, and transforms to a new structure at even greater depth, approximately 2700 km depth, just above the Core-Mantle boundary.
During his PhD, C. Langrand, PhD student at the Université de Lille studied the kinetics of such transformation. It is fast on geological timescales: about 10 to 10,000 seconds, depending on pressure and temperature. Thanks to the collaborations in the TIMEleSS project, the authors realized that this includes the timescales of seismic waves. As such, seismic waves can trigger the transformation and, in turn, the transformation can amplify the seismic signal from D” seismic reflections.
These results from a collaboration between the Université de Lille, the université Clermont-Auvergne, the université de Lyon, the Westfälische Wilhelms-Universität, Münster, CNRS, and the PETRA III / DESY synchrotron source were published on 12 decembre 2019 in Nature Communications.
Full reference : C. Langrand, D. Andrault, S. Durand, Z. Konôpková, N. Hilairet, C. Thomas, S. Merkel, Kinetics and detectability of the bridgmanite to post-perovskite transformation in the Earth’s D″ layer, Nature Communications, 10, 5680 (2019) [doi: 10.1038/s41467-019-13482-x].
Frederica Rochira was at the EGU General Assembly 2019 in Vienna. EGU brings together geoscientists to one meeting covering all disciplines of the Earth, planetary and space sciences. The meeting is held yearly in Vienna, Austria, and, in 2019, it was attended by 16,273 scientists from 113 countries.
Frederica Rochira presented her works entitled Detecting structures in the mid mantle using out-of-plane signals in the multidisciplinary session Dynamics of the mantle in the Earth and planetary bodies: from magma oceans to the present day.
The session, co-organized by TIMEleSS members, included four oral presentations on Thursday as well as 12 PICO presentations early afternoon on Friday. The session was an opportunity for scientists of various fields of geosciences (seismology, geodynamics, mineral physics) to present the results of her works and discuss their implications for understanding the dynamics of mantles, on Earth and other planetary bodies.
Matthias Krug and Frederica Rochira gave presentation in front of their institute in Münster.
Matthias presented his work on Jan 8th and Frederica on Jan 21st. These presentations were an opportunity for the students to display their works in front of their colleagues, get feedback, and new ideas for their project.
Federica Rochira and Matthias Krug presented posters at the Deep Earth Mini Symposium in Münster. The symposium was organized by TIMEleSS PI Tine Thomas.
This one-day meeting attracted an international and interdisciplinary group of deep Earth scientists, PhDs and Master students, with keynote talks given by Jennifer Jackson (Caltech), Jeroen Ritsema (University of Michigam) and Sebastian Rost (University of Leeds), and a poster session with wine and cheese.
The full program of the symposium can be found online in the following document.
In June 2018, Tine Thomas went to Werner Von Siemens Gymnasium in Gronau to introduce geophysics to the pupils.
Thirty students attended and asked many questions. Will they be our new TIMEleSS members?!
Federica Rochira gave her first talk at the Institute of Geophysics in Münster. She presented her part of the TIMEleSS project and the first results about the out-of-plane reflections in the mid-mantle. The seismology group of Münster was present but also Carmen and Matthias of the Institute of Mineralogy, also involved in the TIMEleSS project.