Constraining Two Prominent Low-Velocity Anomalies in the Lower Mantle beneath Africa and Pacific

研究者建议绘制出非洲和太平洋下地幔两个突出的低速异常的详细结构和速度特征。他将使用2D混合方法进行广泛的波形建模，以约束来自不同方向、不同地震相位的地震异常的地震速度、几何形状和长度尺度。PI还建议在这个研究项目的过程中开发一个三维混合地震代码。三维混合代码将用于正演验证二维混合方法波形建模得到的地震结果的有效性。该建议的知识价值包括地震学的观测和理论两个方面。观测方面包括高质量异常地震数据的收集、识别、解释和建模，以绘制下地幔两个突出的低速异常的详细特征为科学目标。该建议的理论方面包括系统研究地震波在非均质地幔中的传播，详细模拟异常地震数据，以及开发三维混合方法。该研究对进一步认识地球的形成演化、地幔热化学对流、核幔边界性质以及“DUPAL异常”等地球化学储层的成因具有重要意义。新的三维代码将在地震学领域有广泛的应用。

WenThe investigator proposes to map out detailed structural and velocity features of the two prominent low-velocity anomalies in the lower mantle beneath Africa and the Pacific. He will use extensive waveform modeling by the 2D hybrid methods to constrain the seismic velocities, geometry, and length-scale of the seismic anomalies from various directions using various seismic phases. The PI also proposes to develop a three-dimensional hybrid seismic code along the course of this research program. The three-dimensional hybrid code will be used to forward verify the validity of the seismic results obtained from the 2D-hybrid method waveform modeling. The intellectual merits of the proposal include both observational and theoretical aspects of seismology. The observational aspect of the proposal includes collection, identification, interpretation and modeling of high-quality anomalous seismic data, with a scientific goal of mapping detailed features of the two prominent low-velocity anomalies in the lower mantle. The theoretical aspect of the proposal includes systematic studies of seismic wave propagation in a heterogeneous mantle, detailed modeling of the anomalous seismic data, and the development of a 3D hybrid method. The proposed research has broad impacts on our further understanding of the formation and evolution of the Earth, thermal-chemical convection in the mantle, the nature of the core-mantle boundary, and the origin of some geochemical reservoirs, such as "the DUPAL anomaly". The new 3D code will have broad applications in the seismology community.