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

研究核幔边界和D”层的小尺度结构将有助于约束该边界层的化学非均质性特征。诸如导热系数和导电性等重要参数取决于材料的微观结构。在常规地震成像方法分辨率限制下，地震波散射是研究非均质性的理想工具。辐射传递理论和波动理论对于地球深部的研究都有各自的优点和局限性。通过耦合辐射传输和波模拟，我们将能够研究靠近CMB的确定性公里尺度结构对远高于1Hz的地表地震记录的影响。通过在目标区域进行波场模拟，我们将测试D ‘ ’和CMB非均质性的不同情况，例如在D ‘ ’中分层或在外核顶部分层，3D非均质性和CMB地形。波模拟的灵活性将允许直接将矿物物理和地球动力学建模中有关潜在非均质性的知识纳入模型，并评估包括所有波效应（如干涉和折射）在内的响应。利用传递理论模拟地震能量从地壳震源到目标区域再返回地面接收器的传播，解锁了目前三维波场模拟无法获得的1Hz以上的频率范围。上地幔和地壳非均质性的影响可以很容易地纳入到转移模拟中，以解释地壳和上地幔散射对高频地震记录的重要影响。全球数千个台站记录的相当数量的极深大地震的可用性，为PP DeepDyn的主题“下地幔和地核的组成、结构和性质”提供了绝佳的机会，提供了低于常规地震方法范围的长度尺度的信息。

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.