2023 Fiscal Year Research-status Report
Earth History Revealed by Iron Electrons in Dense Core-Mantle Boundary Provinces
| Project/Area Number |
23K03524
|
|---|
| Research Institution | Tokyo Institute of Technology |
|---|
Principal Investigator |
ハウザー クリスティーン 東京工業大学, 地球生命研究所, 特任助教 (20723737)
|
|---|
| Project Period (FY) |
2023-04-01 – 2026-03-31
|
| Keywords | Earth composition / global seismology / core-mantle boundary / mineral physics / mantle dynamics |
|---|
| Outline of Annual Research Achievements |
I am advising two graduate student projects: 1) developing a machine learning algorithm to detect the onset of P- and S-wave arrivals in global seismograms and 2) examining details of seismic reflections in the region above the core-mantle boundary. For project (1), the student has adapted an attention-based machine learning algorithm for detecting local earthquakes to the global seismic network for measuring the travel times of P- and S-waves for large events. For project (2), I initiated a collaboration with seismologists at the University of Munster in Germany who are experts in detecting the reflections of seismic waves in the deep mantle. Our groups are collecting studies that record the height of the seismic reflectors above the core-mantle boundary. We are in a unique position to develop globally consistent maps of lower mantle seismic properties.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The research is progressing smoothly. Working with the graduate students, we are prepared to develop two novel seismic data catalogs which will reveal the material properties of lower mantle minerals. For the mineralogical work, I attended the Ehime University Geodynamics Research Center summer workshop where I discussed how iron can exist as a metal, or in its oxidized forms FeO or Fe2O3 in the lower mantle. I organize a discussion group to examine how Earth's initial mantle oxidation state effects the early atmosphere composition and the emergence of life. The discussions have revealed many inconsistencies in the research regarding the oxidation state of the mantle and early Earth. We are designing new methods for systematizing the evolution of Earth's oxidation state.
|
| Strategy for Future Research Activity |
The future plan is to use the new catalog of P- and S-wave arrivals to directly measure velocity variations in the lowermost mantle from the shape of the travel times as a function of distance, the travel-time curve, in different highly-sampled regions along the core-mantle boundary. Preliminary results will be presented at the Studies of the Earth's Deep Interior meeting in America in June. These velocities combined with the new catalog of seismic reflector heights provide the means to distinguish whether iron in lower mantle bridgmanite exists dominantly in Fe2+ or its more oxidized Fe3+ state. I will then use the results from the seismology study to model how the Earth evolved into its present state and examine the implications for the early Earth surface environment.
|
| Causes of Carryover |
The funds allocated for the next fiscal year (including funds from FY23 which were carried over due to purchasing items at a discounted price) support PI Houser and student Jun Su to present research at the Studies of the Earth's Deep interior meeting, which takes place every 2 years, and will be held in Massachusetts, USA in the summer of 2024. We will demonstrate how the new catalog of long period P-wave and S-wave travel times provides new constraints on deep mantle composition and dynamics. PI Houser will also meet with Kate Rychert and Nicholas Harmon at Woods Hole Oceanographic Institute to compare the deep mantle influence on plate tectonics between the Pacific and Atlantic oceans.
|
