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

这个在北纬8到10度的东太平洋隆起上进行的“暗射”实验，将利用地震速度、衰减和Pn到达的异常（如果观测到的话），以及Sn波的异常，绘制出地壳底部附近沿脊轴垂直分布的千米尺度变化。Pn速度各向异性的大小和方向将用于约束莫霍附近的地幔流动方向。该项目的目标是：(1)绘制整个板块上地幔地震速度和衰减结构的沿轴变化图；(2)绘制上地幔各向异性的方向和大小图；(3)确定三个对比点上最下层地壳、莫霍过渡带和上地幔直接位于吸积轴下的垂直结构图；(4)测量整个转换界脊段上地壳厚度变化图。(5)将分割结果与已有的观测值和分割模型进行比较。

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.