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之间的合作建议，以解决三个主要问题。(1)太平洋岩石圈和上地幔的温度结构是什么？(2)一些比较突出的温度变化的动力学原因是什么？特别是，动力学在很大程度上是由近地表物理过程（例如，热边界层不稳定性或TBI）控制的，还是由发生在地球深处的过程（热点羽流，大规模上升流）控制的，还是由深层和浅层过程之间的相互作用控制的（例如，羽流激发热边界不稳定性）？(3)在径向和方位角各向异性方面有什么补充信息？这些问题部分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期间扩散冷却，然后在70至100 Ma期间在太平洋中部重新加热，主要在70至150公里的深度之间。新的地球动力学模拟表明，TBI在板块冷却时自然形成，并可能在观测到的太平洋板块冷却历史中起重要作用。地震学研究将继续发展数据集和理论方法，以改进海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海洋岩石圈与上地幔之间的动力学相互作用。将特别强调太平洋岩石圈的两阶段冷却是如何发生的，是什么控制了它，以及为什么它不会发生在其他海洋下面。特别感兴趣的是TBI是如何开始和演变的，岩石圈是如何侵蚀和再加热的，是什么控制了这一过程的效率，以及TBI和热羽流之间的相互关系。研究生和本科生研究人员将在地球动力学和地震学建模之间的界面工作。此外，该研究将提供海洋上地幔的概要视图，这将对许多新的和正在进行的计划有价值，如边缘、脊2000和海洋地幔动力学（OMD）。

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).