CSEDI Collaborative Research: Anelastic properties of the Earth from seismic to tidal timescale

地震产生的声波穿过地球内部，从而对其路径沿线的情况进行采样。收集到的大量到达的声波被用来重建地球内部的状况和结构。当这些波穿过岩石内部时，它们所穿过的岩石会产生微小的应变。岩石对这些应变的反应取决于温度和化学环境等条件。发生在俯冲带的大地震，例如2004年的安达曼-苏门答腊地震或1964年的阿拉斯加地震，产生的能量足以让地球“像钟一样响”。地球与月球和太阳的引力相互作用（潮汐）导致整个地球的周期性变形，其影响可与大地震相媲美。类似于地震和潮汐引起的微观应变可以在实验室中进行研究，从而也可以研究温度和化学环境对反应的影响。所提出的工作的挑战是将实验室结果应用于地震学和大地测量学的全球观测。这种方法的前景是提高我们对地球内部条件及其物理描述的理解。这些发现将对模拟自上一个冰河时代以来地球表面正在进行的反弹，影响海平面变化原因的确定，以及其他行星和卫星的潮汐模型产生影响。研究人员建议在广泛的时间尺度上结合对小应变变形的观测，从地震体波（秒）到正常模式（分钟-小时）和潮汐（小时到年），以确定地球内部能量耗散的频率依赖性。这些观测结果将结合在一个包括非弹性的非球形地球的正常模式/潮汐模型中。该模型的结果将与实验室导出的晶体颗粒及其缺陷的非弹性行为模型进行比较，这些模型是实验可访问参数空间之外预测的基础。将实验预测与全球模型进行比较，将有助于限制微物理模型对由地震波和潮汐引起的小应变变形的适用性，并最终限制冰川后反弹和（大应变）对流的适用性。同时，正态模态和潮汐信息的结合将对中、下地幔的条件和结构产生新的约束，这是其他方法难以获得的。

Earthquakes produce sound waves that travel through the interior of the Earth and thereby sample the conditions along their paths. Collections of large numbers of arriving sound waves are used to reconstruct conditions and structure of the interior of the Earth. While traveling through the interior, these waves produce microscopic strains in the rocks they pass through. The response of the rocks to these strains depends on conditions such as temperature and chemical environment. Very large Earthquakes in subduction zones, for example the Andaman-Sumatra earthquake from 2004 or the Alaskan earthquake from 1964, produce enough energy for the Earth to "ring like a bell". Gravitational interaction of the Earth with the Moon and the Sun (tides) causes periodic deformation of the whole Earth that is comparable to the effects of large Earthquakes. Microscopic strains similar to those caused by earthquakes and tides can be investigated in the laboratory, and thereby also the effects of temperature and chemical environment on the response. The challenge of the proposed work is to apply the laboratory results to global observations from seismology and geodesy. The promise of this approach is to improve our understanding of the conditions in the interior of the Earth and its physical description. The findings will have implications for modeling of the ongoing rebound of the surface of the Earth since the last ice age, affecting determination of the causes of changes in sea level, as well as tidal modeling of other planets and moons.The investigators propose to combine observations of small-strain deformation at a broad range of timescales, from seismic body waves (seconds) to normal modes (minutes - hour) and tides (hours to years), to determine the frequency dependence of energy dissipation in the interior of the Earth. These observations will be combined in a normal mode/tidal model of a non-spherical Earth that includes anelasticity. Results from this model will be compared to laboratory-derived models for anelastic behavior of crystalline grains and their defects, which are the basis for predictions outside of the experimentally accessible parameter space. Comparison of experimental predictions with global models will help to constrain the applicability of the microphysical models to small-strain deformation due to seismic waves and tides, and ultimately also post-glacial rebound and (large-strain) convection. At the same time the combination of information from normal modes and tides will yield new constraints on the conditions and structure in the mid to lower mantle, which are difficult to obtain by other means.