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

研究核幔边界(CMB)和D‘’层的小尺度结构将有助于约束该边界层的化学不均匀特征。热导率和电导率等重要参数取决于材料的微观结构。地震波散射是研究常规地震成像方法分辨率极限以下非均质性的理想工具。辐射传输理论和波动理论在地球深部研究中各有优势和局限性。通过耦合辐射传输和波浪模拟，我们将能够研究接近CMB的确定的千米尺度结构对远高于1赫兹的地面地震记录的影响。利用目标区域的波场模拟，我们将测试D‘’和CMB非均质性的不同情况，如D“‘或外核顶部分层、3D非均质性和CMB地形。波浪模拟的灵活性将允许将矿物物理和地球动力学模拟中关于潜在非均质性的知识直接纳入模型，并评估包括所有波浪影响的响应，如干扰和折射。利用传递理论模拟地震能量从地壳中的震源传播到目标区，再返回到地表接收器的过程，解锁了目前三维波场模拟无法获得的1赫兹以上的频率范围。上地幔和地壳非均质性的影响可以很容易地纳入到传输模拟中，以解释高频地震记录由于地壳和上地幔散射而经历的重要修改。全球数千个台站记录到的合理数量的极深大地震的可用性，为利用低于传统地震方法范围的长度尺度的信息对PP DeepDyn的“下地幔和核的组成、结构和性质”这一主题作出贡献提供了绝佳的机会。

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.