DeepDynSeminar #1: Christine Thomas

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Prof. Christine Thomas (University of Münster) kicks off our SPP2404 DeepDyn seminar series with a lecture on "Seismic structures at the CMB". The lecture will take place in English.

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Seismic structures at the CMB

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Abstract

Understanding structure and mineralogy in the lowermost Earth's mantle (D" layer) provides important constraints on mantle and core dynamics. Especially the reflection off the D" layer has been used in the past to constrain the depth of this layer, and to determine the mineralogy within D". Using additional observations of polarities of these waves allows a better understanding of velocity (and density) changes across the D" reflector. Furthermore, using the polarities of D" reflections in combination with shear wave splitting of ScS waves that traverse the D" layer, we can determine the style of deformation in this layer which provides further knowledge on mantle flow. Detection of D" anisotropy is usually carried-out with shear wave splitting analysis alone. To constrain azimuthal anisotropy and infer mineralogy and deformation style, a number of crossing paths is usually necessary. But when we use the approach that utilises the polarity of P- and S- wave reflections from the D" discontinuity, compared with the main phases P and S, and combine these measurements with ScS splitting results, we find that azimuthal coverage is less important. Using deformation scenarios for a number of lower(most) mantle candidate materials, we calculate the reflection coefficient for P and S-wave reflections and ScS splitting predictions and find that we can constrain the mineralogy responsible for the D" reflection and anisotropy in several regions.

Link to the next seminar series lecture

Short stories on traveling crust to core with a bright lamp: white-laser spectroscopy for physical properties of the deep Earth