Seismic and Geodynamic Investigation of the Interaction Between the Oceanic Lithosphere and Upper Mantle

这是地震学家和地球动力学家共同提出的解决三个主要问题的建议。(1)太平洋岩石圈和上地幔的温度结构是什么？(2)一些比较显著的温度变化的动力原因是什么？特别是，动力学主要是由近地表物理过程(例如，热边界层不稳定性或TBI)控制的，还是由成因位于地球更深处的过程(热点羽流、大规模上升流)控制的，还是由深层和浅层过程(例如，羽流激发的热边界不稳定性)之间的相互作用控制的？(3)在径向和方位向各向异性中有哪些补充信息？这些问题在一定程度上是由太平洋热结构的初步模型引起的，该模型揭示了太平洋岩石圈经历了一个断断续续的冷却历史，在最初的70 Ma时扩散冷却，然后在70至100 Ma之间在中太平洋重新加热，主要在70至150公里的深度。新的地球动力学模拟表明，大洋板块冷却时会自然形成大洋上地幔，并可能在观测到的太平洋板块冷却历史中发挥重要作用。地震学研究将继续发展数据集和理论方法，以改进大洋上地幔的地震和温度模型。地球动力学研究的目的是了解大洋岩石圈和上地幔之间的动力学相互作用。将特别强调为太平洋岩石圈推断的两阶段冷却可能如何发生，是什么控制着它，以及为什么它可能不会发生在其他海洋之下。特别感兴趣的是热暴流如何启动和演化，羽流如何侵蚀和重新加热岩石圈，是什么控制了这一过程的效率，以及热暴流之间的相互关系。一名研究生和本科生研究人员将在地球动力学和地震学模型之间的交界处工作。此外，这项研究将提供大洋上地幔的概貌，这将对一些新的和正在进行的倡议，如边缘、海脊2000和大洋地幔动力学(OMD)有价值。

This is a collaborative proposal between seismologists and geodynamicists to address three major questions. (1) What is the temperature structure of the Pacific lithosphere and upper mantle? (2) What are the dynamical causes of some ofthe more prominent temperature variations? In particular, are the dynamics controlled largely by near-surface physical processes (e.g., thermal boundary layer instabilities or TBI), by processes whose genesis lies deeper within the earth (hot-spot plumes, large-scale upwellings), or by interactions between deep-seated and shallow processes (e.g., plumes exciting thermal boundary instabilities)? (3) What complementaryinformation is available in radial and azimuthal anisotropy? These questions are motivated, in part, by a preliminary model of the thermal structure of the Pacific that reveals that the Pacific lithosphere has experienced a punctuated cooling history, cooling diffusively for its first 70 Ma and then reheating in the Central Pacific between ages of 70 and 100 Ma predominantly at depths between 70 and 150 km. New geodynamical simulations show that TBI forms naturally as the plate cools and may play an important role in the observed cooling history of the Pacific plate.The seismological research will continue to develop data sets and theoretical methods to improve the seismic and temperaturemodels of the oceanic upper mantle. The geodynamic research will aim to understanding the dynamic interplay between the oceanic lithosphere and upper mantle. Particular emphasis will be placed on how the two-stage cooling inferred for the Pacific lithosphere may occur, what controls it, and why it may not occur beneath other oceans. Particular interest is in how TBI initiate and evolve, how plumes erode and reheat the lithosphere and on what controls the efficiency of this process, and the interrelation between TBI and thermal plumes.A graduate student and undergraduate researchers will work at the interface between geodynamical and seismological modeling. In addition, the research will provide a synoptic view of the oceanic upper mantle that will be valuable for a number of new and on-going initiatives such as Margins, Ridge2000, and Ocean Mantle Dynamics (OMD).