Waveform inversion for localized 3-D structure in D"

随着距离核幔边界（CMB）的减小，D”内的温度和化学成分变化迅速。D”中的物质和能量通量数据可以为理解地球动力学和演化提供重要信息，但迄今为止，D”的三维（3-D）结构还没有足够高的分辨率。本文提出了一种直接反演高分辨率三维地球结构地震波形的新方法。然后，这项研究将新的反演方法应用于北美洲地震台站记录的南美洲地震的大量地震波形数据集，以确定中美洲地幔最低层的地震结构。这项研究发现了证据，证明在中美洲之下的D”中存在着法拉隆板块俯冲的残余。这些物质通过地幔对流从地球表面带到D”。

The temperature and chemical composition within D" vary rapidly as the distance to the core-mantle boundary (CMB) decreases. Data on material and energy flux in D" can provide important information for understanding the Earth's dynamics and evolution, but the three dimensional (3-D) structure of D" was not heretofore known with sufficiently high resolution. The present study has developed a new method for direct inversion of seismic waveforms for high-resolution 3-D Earth structure. The study then applied the new inversion method to a large data set of seismic waveforms recorded at seismic stations in North America for earthquakes under South America to determine seismic structure in the lowermost mantle under Central America. The study found evidence for the existence of remnants of the subducted Farallon Plate in D" beneath Central America. This material was carried from the Earth's surface to D" by mantle convection.