Collaborative Research: Imaging small-scale convection and structure of the mantle in the south Pacific: a US contribution to international collaboration PacificArray

地球表面的所有变形，包括导致地震的断层作用，都是由构造板块的运动产生的。人们普遍认为，地幔中的热对流驱动着板块的运动，但这种对流的细节以及它是如何准确地移动板块的，人们知之甚少。海洋板块占地球表面的70%，是了解地幔对流的重要窗口，但由于缺乏来自海洋盆地的地震数据，它们在很大程度上没有被勘探。关于大洋板块的热结构，大洋板块中部火山活动的重要性，以及板块下方对流的地幔如何控制它们的运动，问题比比皆是。重力场中的波和不明原因的海底变浅暗示了大洋板块下方的小范围对流。该项目有助于在太平洋盆地战略性地放置记录地震能量的临时仪器阵列的国际努力。社区在海底地震仪方面的最新进展将被用来在目前存在较大覆盖差距的地点记录独特的数据集。这些数据将使我们能够推断与小规模对流有关的地幔温度的变形和变化。作为国际合作的一部分，所有数据都将向世界各地的科学家开放。该项目支持研究生和本科生的培训。该项目将在中太平洋和南太平洋的两个30站阵列中收集12-15个月的宽带海底地震仪(OBS)数据。这些阵列部署在两个不同的板块年龄(~30 Ma和~120 Ma)，将解决关于大洋软流圈动力学的具体关键问题，包括其基本状态(温度、是否存在熔融、水或其他挥发物，以及变形机制)。这些阵列的设计是为了成像小尺度对流的各向异性速度特征，这一特征被用来解释在旧海洋板块、140-200公里波长的重力线条以及在各种尺度上观察到的无处不在的离轴、无羽流火山活动中年龄随深度曲线变平的原因。各向异性面波和体波层析模型将补充横波分裂和衰减测量，以获得对软流层和板块底部的多方面了解。最后，中南部太平洋表面波和体波路径覆盖率的数量级增加将使全球层析成像取得新的进展。

All deformation on the surface of Earth, including faulting responsible for earthquakes, is produced by the motion of tectonic plates. It is widely accepted that thermal convection in the mantle drives plate motion, but details of that convection and how exactly it moves the plates are poorly understood. Oceanic plates make up 70% of the Earth's surface and offer important windows into mantle convection, yet they are largely unexplored due to the lack of seismic data from the ocean basins. Questions abound regarding the thermal structure of oceanic plates, the significance of volcanism in the middle of oceanic plates, and how the convecting mantle beneath the plates controls their movements. Waves in the gravity field and un-explained shallowing of the ocean floors hint at small-scale convection beneath the oceanic plates. This project contributes to an international effort to strategically place temporary arrays of instruments across the Pacific Ocean basin that record the energy from earthquakes. Recent community advances in ocean bottom seismographs will be used to record unique datasets in locations where large gaps in coverage exist today. These data will allow us to infer deformation and variations in mantle temperature related to small-scale convection. As part of the international collaboration, all data will be openly available to scientists worldwide. The project supports the training of graduate and undergraduate students.This project will collect 12-15 months of broadband ocean bottom seismograph (OBS) data in two 30-station arrays in the central and southern Pacific. These arrays, deployed at two distinct plate ages (~30 Ma and ~120 Ma), will address specific critical questions on the dynamics of the oceanic asthenosphere, including its underlying state (temperature, presence of melt, water or other volatiles, and deformation mechanism). The arrays are designed to image the anisotropic velocity signature of small-scale convection, which has been invoked to explain the flattening of the age versus depth curve in old ocean plates, 140-200 km wavelength gravity lineations, and ubiquitous off-axis, non-plume volcanism observed at a variety of scales. Anisotropic surface wave and body wave tomographic models will be supplemented by shear wave splitting and attenuation measurements to obtain a multi-faceted understanding of the asthenosphere and base of the plates. Finally, the order-of-magnitude increases in path coverage for surface and body waves in the south-central Pacific will enable new advances in global tomography.