The ' D" ' refers to the lowermost 200 km in the mantle and was named such by Bullen in 1953. This region is distinct from the rest of the lowermost mantle, because it appears to contain some very heterogeneous features. The study of the D" in our group is two fold. On one side we attempt to link predictions of flow combined with plausible mineralogical compositions to explain observations of seismic anisotropy in the lowermost lower mantle. On one side we forward model waveforms through models with sharp boundaries and strong heterogeneity to fit waveform complexities observed in real data. The sharp boundaries in seismic velocities and the occurrence of ultra-slow patches are suggestive of chemical heterogeneity. On the other side we attempt to link predictions of flow combined with plausible mineralogical compositions to explain observations of seismic anisotropy in the lowermost lower mantle.
Modeling strong heterogeneity in the D"
Lekic, V., S. Cottaar, A.M. Dziewonski, B. Romanowicz, Permian Anomaly: a new class of lower mantle structure, in review.
To, A., Romanowicz, B., Capdeville, Y., & Takeuchi, N., 2005. 3d effects of sharp boundaries at the borders of the african and paciﬁc superplumes: Observation and modeling, Earth Plan. Sci. Lett., 233(1-2), 137–153.
Multidisciplinary approach to explain seismic anisotropy in the D"
This project is in collaboration with Allen McNamara and Mingming Li at ASU on the geodynamical work and Rudy Wenk at UC Berkeley, and Carlos Tome at Los Alamos, on the modeling of polycrystal behaviors.
Hans-Rudolf Wenk, Sanne Cottaar, Carlos N. Tome, Allen McNamara, Barbara Romanowicz, Deformation in the lowermost mantle: From polycrystal plasticity to seismic anisotropy, Earth and Planetary Science Letters, Volume 306, Issues 1-2, 1 June 2011, Pages 33-45, ISSN 0012-821X, DOI: 10.1016/j.epsl.2011.03.021.