HighWInD: High Frequency Wave INteraction with the D'' Layer

Project description

Investigating the small scale structure at the core mantle boundary (CMB) and in the D’’ layer will help to constrain the characteristics of chemical heterogeneities in this boundary layer. Important parameters such as the thermal and electric conductivities depend on the micro structure of the material. Seismic wave scattering is the ideal tool for the investigation of heterogeneity below the resolution limit of conventional seismic imaging methods. Radiative transfer theory and wave theory both have their advantages and limitations for the investigation of the deep Earth. By coupling radiative transfer and wave simulations we will be able to study the effects of deterministic kilometer scale structure close to the CMB on surface seismograms well above 1Hz. Using wavefield simulations in the target region we will test different scenarios of D’’ and CMB heterogeneity such as layering in D’’ or stratified layers at the top of the outer core, 3D heterogeneity and CMB topography. The flexibility of wave simulations will allow to directly incorporate knowledge about potential heterogeneities from mineral physics and geodynamic modeling into the model and evaluate the response including all wave effects such as interference and refraction. Simulating the propagation of the seismic energy from the earthquake source in the crust to the target region and back to the surface receiver using transfer theory unlocks the frequency range above 1Hz that is currently not accessible to 3D wavefield simulation. The effects of upper mantle and crustal heterogeneity can be readily incorporated in the transfer simulations to account for the important modifications that high frequency seismograms experience due to scattering in the crust and upper mantle. The availability of a reasonable number of very deep large earthquakes that have been recorded at thousands of stations globally provides the perfect opportunity to contribute to the theme “The composition, structure and properties of the lower mantle and core” of the PP DeepDyn with information on length scales below the range of conventional seismic methods.