Seismological Studies of Convection Beneath the Plates

绘制板块下方的对流模式对于我们理解地球内部的热传递模式、地幔的化学分化和演化、地幔的粘性结构以及驱动板块构造的力是至关重要的。最近在通过对流对地震速度的影响直接绘制这种模式方面取得了很大进展。预计会有两种速度变化：与成分或温度有关的横向非均质性，以及与流动过程中的变形有关的组构或晶体取向引起的各向异性。这里提出的研究的目的是绘制与板块下方对流有关的上地幔速度结构图，特别侧重于检验特定区域存在各向异性的假设，以及使用以在其他方式无法进入的地区提供高横向分辨率的方式对地球进行采样的相来绘制小尺度(波长500至3000公里)特征图。

Mapping the pattern of convection beneath the plates is central to our understanding of the mode of heat transfer within the earth, the chemical differentiation and evolution of the mantle, the viscosity structure of the mantle, and the forces that drive plate tectonics. Much progress has recently been made toward directly mapping the pattern through the effects of convection on seismic velocities. Two types of velocity variations are expected; lateral heterogeneities related to composition or temperature, and anisotropy caused by fabric or crystal alignment associated with deformation during flow. The purpose of the research proposed here is to map velocity structures in the upper mantle related to convection beneath the plates, with particular emphases on testing hypotheses of the existence of anisotropy in specific regions and on mapping small- scale (wavelengths 500 to 3000 km) features using phases that sample the earth in ways that provide high lateral resolution in otherwise inaccessible areas.