Annie Souriau

Annie Souriau is a French seismologist from the commune of Saint-Cloud Paris. She is primarily known for her research into Earth's inner and outer cores, specifically her work examining seismic activity within and around the Pyrenees mountains. Through her and her colleague's research and studies, she has made notable advances to how humans understand the inner workings of the Earth's core while also winning many awards in the process.

Education and career Annie Souriau began her Education at École normal supérieure de Fontenay-aux-Roses, which was reserved as a school for girls, during that time her specialty was physics. She then moved onto Institut de Physique du Globe in Paris where she obtained her Ph.D. in 1978. in seismology on the structure of the upper mantle. After completing this Souriau then moved on to Toulouse in 1979 to work with the Geodesy Research Group, where alongside and led by Michel Lefebvre, they created a CNRS structure which was used to create a link between fundamental research and space experiments in Earth physics. She spent 1983 to 1984 at Harvard University, followed by a six-month period in Canberra.

Research leftSouriau is known for her combination of observational data and modeling to examine the structure of Earth's internal core, particularly within the Pyrenees mountains. She has also examined how earthquakes and the drift of the Earth's pole interact with the Chandler wobble, and the heterogeneous nature of the mantle and how it interacts with the surface topography of Earth.

Used a top-down and bottom-up approach to determine the changing rotation of the inner core. Samples of seismic waves were taken, when observed, it appears that the core did not have a cylindrical symmetry. The top-down approach showed that the inner core anisotropy reflects cylindrical symmetry. The axis of the inner core is not perpendicular to orbit, but rather tilted. The rotation affects the direction of anisotropy which results in a change in propagation times. The bottom-up approach first observed the differing anisotropy. The rotation is found to be affected by the changing anisotropy that occurs under seismic waves.

One of the questions that Annie was researching was whether or not there was an existing structure within the outer liquid core. The possible situation that could explain the presence of another structure are eigenmodes and the anisotropy that abnormally splits the eigenmodes. Souriau conducted her research predominantly looking at anisotropy and eigenmodes within the outer liquid. She looked for anisotropy within the outer liquid core by using data from PKPdf polar rays. After, she looked for heterogeneities that would lie still underneath the polar caps which are located at the core mantle boundary. The conclusion of her research was she could not find any splitting eigenmodes within the outer liquid core.

Through Annie's research she has looked at seismic phases by analyzing patters in travel times and how they reflect/traverse off the Earth’s core. She has aided in discovering three important concepts concerning the Earth’s inner core over the last three decades. The first discovery is that the inner core is elastically anisotropic and has a symmetrical axis that is aligned with the rotational axis of Earth. The second discovery is that there is hemispherical elastic heterogeneity in the Earth’s inner core and lastly the solid mantle above, rotates slower than the Earth’s inner core. Souriau predicted that the Earth’s outer core was homogeneous and presented evidence that the base was heterogeneous and used that idea to investigate the connections between the heterogeneous mantle and the dynamics with the topography of the Earth’s surface. Due to Annie’s findings, she was the recipient of the 2019 EGU Gutenberg Medal.

Selected publications

Annie Souriau, J. H. Woodhouse; A strategy for deploying a seismological network for global studies of Earth structure. Bulletin of the Seismological Society of America 1985;; 75 (4): 1179–1193. doi: https://doi.org/10.1785/BSSA0750041179 Spatial variations of b-value and crustal stress in the Pyrenees, A. Rigo &A. Souriau &M. Sylvander, (October 2017) Deep Earth Structure: The Earth's Cores, Member, Academia Europaea (2004) Inaugural winner of the Réseau Accélérométrique Permanent (RAP) award (2018) Prize Binoux of the French Academy of Sciences (1989) Corresponding member of the Bureau des longitudes, Paris (2010)