Studies of Terrestrial Gravity Using Superconducting Gravimeters

使用超导重力仪研究地球重力

• 批准号: 0409381
• 负责人: David Crossley
• 金额: $ 19万
• 依托单位: Saint Louis University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-15 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409381&HistoricalAwards=false
• 关键词: Studies; Terrestrial; Gravity; Using; Superconducting

This project consists of two separate studies using high precision gravity data collected by the network of superconducting gravimeters (Global Geodynamics Project, or GGP). The first is a comparison between the high precision monthly gravity field that is now available from the GRACE (Gravity Recovery and Climate Experiment) satellite mission and the 7 ground-based GGP stations in Europe. The intellectual merit is in using for the first time both data sets, even though they differ considerably in spatial and temporal resolution, to identify the time variation of the hydrology over central Europe. Studies done by the author and his colleagues have demonstrated that both data sets have a common signal that appears to correlate well with the predicted moisture content of the ground. This correlation will be further explored to determine where the signal comes from and to what extent the ground stations are able to validate the satellite-based models. This is a unique study because of the independence of the two observational techniques. The broader impact of the GRACE experiment is that it will provide extremely useful data for a wide variety of geophysical problems such as the accurate assessment of continental water storage for long-term planning of global water resources.The second study will use all the GGP data (20 stations), over the last 7 years, to search for several signals from the Earth's deep interior, particularly the Slichter triplet. This triplet arises from the oscillations of the Earth's inner core (IC) within the fluid outer core, when excited by an energetic source such as an earthquake; the splitting into 3 modes comes primarily from Earth rotation. The motions are extremely small - about one mm or less, but in principle detectable using the GGP gravity array. The intellectual merit of the study is to find the density jump between the inner and outer cores at the boundary (ICB). This jump is crucial for assessing the energetics to the Earth's magnetic field generation, i.e. how much energy can come from the latent heat of freezing of the IC as it grows in time. Recent estimates of the ICB density jump have varied between 0.3 and 0.8 Mg m-3, using methods such as differential scattering of seismic body waves from the ICB and from the frequencies of the normal modes of the Earth. The broader impact of this project is in graduate education, through student support for 3 years. This new study will strengthen considerably the graduate student program at St. Louis University.

该项目包括两项独立的研究，使用超导重力仪网络（全球地球动力学项目，或GGP）收集的高精度重力数据。第一个是GRACE（重力恢复和气候实验）卫星使命和欧洲7个地面GGP站提供的高精度月重力场之间的比较。智力上的优点是第一次使用这两个数据集，即使它们在空间和时间分辨率上有很大差异，以确定中欧水文的时间变化。作者和他的同事所做的研究表明，这两个数据集有一个共同的信号，似乎与预测的地面含水量很好地相关。将进一步探讨这种相互关系，以确定信号来自何处以及地面站能够在多大程度上验证卫星模型。这是一项独特的研究，因为这两种观察技术是独立的。GRACE实验的更广泛的影响是，它将为各种地球物理问题提供极其有用的数据，例如为全球水资源的长期规划准确评估大陆水储存量，第二项研究将使用过去7年的所有GGP数据（20个站），以寻找来自地球深部内部的几个信号，特别是Slichter三重态。这种三重态是由地球内核（IC）在流体外核内的振荡产生的，当被能量源（如地震）激发时;分裂成3个模式主要来自地球自转。这些运动非常小--大约一毫米或更小，但原则上可以使用GGP重力阵列检测到。该研究的智力价值是找到边界（ICB）处内外核之间的密度跳跃。这种跳跃对于评估地球磁场产生的能量学是至关重要的，即随着时间的推移，有多少能量可以来自IC的冷冻潜热。最近估计的ICB密度跳跃变化之间的0.3和0.8 Mg m-3，使用的方法，如差分散射的地震体波从ICB和地球的正常模式的频率。该项目的更广泛的影响是在研究生教育，通过学生支持3年。这项新研究将大大加强圣路易斯大学的研究生项目。