Heterogeneities, Anisotropy and Attenuation in the Deep Earth through Seismic waveform studies (HAADES)

该项目旨在通过地震观测和模拟的新组合，了解地幔最下部--D“地区地震结构的成因。将差分衰减测量、各向异性和对最低地幔敏感的相速度观测与2D/3D模拟相结合，将对最低地幔矿物学和动力学提供更好的约束。由于深度大，很难进入该地区，而到达如此深的区域的唯一途径是使用地震波。最低地幔的长波结构受到相当一致的限制，但在过去的二十年里，较短的尺度特征被叠加，因此D“区的结构变得更加复杂和有趣。这些较小规模的特征是通过区域研究报告的，这些区域研究没有系统地调查相同的地震参数，而且往往没有尝试将可观测数据组合在一起。因此，D“结构的全球地图仍然无法获得，这将有助于了解其地震结构的起源。这就是为什么我们在这个项目中建议在全球数据集上使用内部一致的技术对各种D”地震属性(各向异性、衰减、地震速度和反射器)进行测量，这些技术将在联合解释中结合在一起。拟议的项目将提高我们对D“区内地震异常的认识，D”区是约束地球动力学和矿物学的关键。我们结合差异衰减、各向异性和反射层深度/速度的方法是独一无二的，其结果预计将对许多学科产生重要影响：它将有助于回答地球动力学问题，如跨越核-地幔边界(CMB)的物质交换和地球的热收支，它还将约束下地幔矿物学。

This project aims at understanding the causes for seismic structures in the lowermost mantle, the D" region, by using a novel combination of seismic observables and modelling. Combining differential attenuation measurements, anisotropy and velocity observables of phases sensitive to the lowermost mantle with 2D/3D modelling will provide a better constraint on the lowermost mantle mineralogy and dynamics. The region is difficult to access due to its large depth and the only way to reach such a deep region is through the use of seismic waves. The long wavelength structure of the lowermost mantle is fairly consistently constrained but during the last two decades shorter length scale features have been overprinted so that the structure of the D" region has become more complex and more intriguing. These smaller-scale features have been reported through regional studies that did not systematically investigate the same seismic parameters and often combinations of observables has not been attempted. A global map of the D" structure is thus still unavailable that would help to understand the origin of its seismic structure. That is why we propose in this project to perform measurements of various D" seismic properties (anisotropy, attenuation, seismic velocities and reflectors) on a global dataset with internally consistent techniques that will be taken together in a joint interpretation. The proposed project will improve our knowledge of the seismic anomalies within the D" region which is crucial to constrain the dynamics and mineralogy of the Earth. Our approach of combining differential attenuation, anisotropy and reflector depths/velocities is unique and the results are expected to have an important impact on a wide variety of disciplines: it will contribute to answer geodynamical questions such as material exchange across the Core-Mantle Boundary (CMB) and heat budget of the Earth and it will also constrain the lower mantle mineralogy.