Collaborative Research: Mapping Melt and Matrix Flow in the Uppermost Mantle: Undershooting the East Pacific Rise between Siqueiros and Clipperton

这项在东太平洋海平面北纬8度至10度之间进行的“俯冲”试验，将利用地震速度、Pn波的衰减和异常，以及如果观测到的锡波，绘制地壳底部附近熔体沿山脊轴垂直分布的公里尺度变化图。Pn速度各向异性的大小和方向将被用来约束莫霍面附近地幔流动的方向。该项目的目标是：(1)绘制整个地段上地幔地震速度和衰减结构的轴向变化图，(2)绘制最上地幔各向异性的方向和大小，(3)确定三个对比点上最下地壳、莫霍面过渡带和最上地幔在吸积轴正下方的垂直结构，(4)测量整个变换边界脊段上地壳厚度的变化，以及(5)将结果与现有的观测和分段模型进行比较。

This "undershooting" experiment, on the East Pacific Rise between 8 and 10 degrees north, will use seismic velocity and attenuation and anomalies of Pn arrivals, and Sn waves if they are observed, to map km-scale variations in the vertical distribution on melt near the base of the crust along the ridge axis. The magnitude and orientation of anisotropy in Pn velocities will be used to constrain the direction of mantle flow near the Moho. The goals of the project are to: (1) map along-axis variations in the seismic velocity and attenuation structure of the uppermost mantle along he entire segment, (2) map the orientation and magnitude of anisotropy in the uppermost mantle, (3) determine the vertical structure of the lowermost crust, Moho transition zone, and uppermost mantle directly beneath the axis of accretion at three contrasting sites, (4) measure crustal thickness variations along an entire transform-bounded ridge segment, and (5) compare the results with existing observations and models of segmentation.