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The Global Seismology Research Group spans across two affiliations: part of the group resides at the Institut de Physique du Globe in Paris, within the Departement de Sismologie. The other part resides at UC Berkeley, within the Department of Earth and Planetary Science and the Berkeley Seismological Laboratory. We keep in touch in various ways, and in particular through weekly video-conferenced group meetings.

Our research focuses on structure and dynamics of the deep earth, from the crust to the inner core. We tackle theoretical wave propagation problems in complex 3D media, including forward modeling and tomographic inversion for elastic as well as anelastic structure. In order to better understand the chemical and thermal state of the mantle and the processes operating therein, we seek to apply the latest findings of the mineral physics community within the context of our seismic probing. We also study earthquake source mechanisms and scaling laws, as well as global seismic moment release and its relation to plate tectonics. One of our recent research directions concerns the Earth's "hum" and the insights it brings to ocean/atmosphere/solid earth interactions.

Our research is supported through a variety of sources: at Berkeley through grants from the NSF/EAR program and from the UC Labfee collaboration program, and in Paris, through the ERC Advanced Grant "WAVETOMO".

Group photo May 2015 at Berkeley, from left to right, Kaiqing Yuan, Alizée DUBOIS, Barbara Romanowicz, Heidi Fuqua, Laura Salmi, Anais Ibourichene, Thomas Bodin, Dorian Soergel, Corinna Roy
Group photo Dec 2013 - after the AGU meeting in San Francisco


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2013: Applying a new waveform imaging methodology that takes advantage of accurate numerical seismic wavefield computations, Barbara Romanowicz's group has constructed a global shear velocity model in the upper mantle that reveals the presence of low velocity channels at the base of the oceanic asthenosphere. In a paper recently published in Science (, graduate student Scott French, former graduate student Vedran Lekic (now assistant professor at the University of Maryland) and Barbara Romanowicz show that these quasi-periodic finger-like structures of wavelength ~2000 km, stretch parallel to the direction of absolute plate motion for thousands of kilometers. Below 400 km depth, velocity structure is organized into fewer, undulating but vertically coherent, low-velocity plume-like features, which appear rooted in the lower mantle. This suggests the presence of a dynamic interplay between plate-driven flow in the low-velocity zone, and active influx of low-rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer. Hotspots are not the direct consequence of plumes impinging on the lithosphere. Abstract and Related Papers Here

View Romanowicz fig3 cropped.jpg

2015: We have now extended this waveform imaging methodology to the WHOLE mantle. The technical details of the resulting whole mantle global shear velocity model (SEMUCB_WM1) can be found in French and Romanowicz (2014, Geophys. J. Int.). This model shows several interesting features. In particular it clearly shows the presence of fat "mantle plumes" extending from the vicinity of the core-mantle boundary through the lower mantle under those hotspot volcanoes that are located over the large low shear velocity provinces (LLSVPs), two major antipodal structures well documented to cover equatorial regions under the Pacific ocean and under Africa. These plumes must be much wider than the classical thermal plumes expected in a purely thermally driven convecting mantle and are likely of thermo-chemical nature, drawing material of different composition from the base of the mantle, and rising through a very sluggish background lower mantle. For more details, see our paper recently published in Nature (French and Romanowicz, 2015, Nature) Abstract and Related Papers Here


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