WHO WE ARE & WHAT WE DO
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".
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 (http://www.sciencemag.org/content/342/6155/227.full), 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
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