An analysis of upper mantle discontinuity structure using 3D synthetics and global network data

天然存在的同位素的放射性衰变（例如，铀、钍和钾）一直是整个地质时期地球内部热量的主要来源。这些热量主要通过地幔中的缓慢（每年英寸）对流逸出。这些洋流是地质活动的原因，包括造山、火山爆发和地震。虽然板块构造是地幔中固态岩石流动的表面表达，但仍然不确定上地幔和下地幔中是否存在单独的对流循环（即，分层对流）或对流是否涵盖整个地幔（即全地幔对流）。了解地幔对流对模拟地球热演化具有重要意义，我们的工作主要集中在410 km和660 km附近的边界。在410公里和660公里的边界处，最丰富的造岩矿物经历了向更致密结构的相变。由于410公里和660公里的矿物相变取决于周围的地幔温度，精确的地图深度的410公里和660公里的过渡作为“温度计”的地幔，可以用来推断地幔流的规模。迄今为止，410公里和660公里过渡带深度的最精确的全球地图是通过处理全球地震仪阵列记录的数千次地震所产生的地震波反射得出的。然而，各研究小组制作的最新地图仍然不一致。它们表现出长波长相对于短波长变化的不同优势和主要异常（即，厚的和薄的过渡区区域）不相干地定位。我们将解决这些不一致的调查文物由于系统的数据处理错误和忽略的影响，从三维波传播的异质地幔。使用最先进的三维地震波传播软件，我们将估计所应用的分析程序中的不确定性，我们将确定预期的410公里和660公里的地形为一系列对流的情况下，地幔。

Radioactive decay of naturally occurring isotopes (e.g., uranium, thorium and potassium) has been a major source of Earth's internal heat throughout geologic time. This heat escapes primarily by slow (inches per year) convection in Earth's mantle. These currents are responsible for geologic activity including mountain building, volcanic eruptions, and earthquakes. While plate tectonics is the surface expression of solid-state rock flow in the mantle, it is still uncertain whether separate convection cycles exist in the upper and lower mantle (i.e., layered convection) or whether convection encompasses the entire mantle (i.e. whole-mantle convection). An understanding of mantle convection is important for modeling the thermal evolution of our planet.The proposed work is focused on boundaries near 410 km and 660 km. At the 410-km and 660-km boundaries, the most abundant rock-forming minerals undergo phase transitions to denser structures. Since the 410-km and 660-km mineral phase transitions depend on the ambient mantle temperature, precise maps of the depths of the 410-km and 660-km transitions act as 'thermometers' of the mantle and can be used to infer the scales of mantle flow. To date, the most precise global maps of the depths of the 410-km and 660-km transitions have been derived from the processing of seismic wave reflections produced by thousands of earthquakes and recorded by global arrays of seismometers. However, the latest maps produced by various research groups remain inconsistent. They exhibit different predominance of long-wavelength versus short-wavelength variations and major anomalies (i.e., thick and thin transition zone regions) are located incoherently. We will address these inconsistencies by investigating artifacts due to systematic data processing errors and ignored effects from 3D wave propagation in the heterogeneous mantle. Using state-of-the-art software for 3D seismic wave propagation, we will estimate the uncertainties in the applied analytical procedures, and we will determine the expected 410-km and 660-km topography for a range of convection scenarios for the mantle.