On the density distribution within the Earth

The distribution of density as a function of position within the Earth is much less well constrained than the seismic velocities. The primary information comes from the mass and moment of inertia of the Earth and this information alone requires that there be a concentration of mass towards the centre of the globe. Additional information is to be found in the frequencies of the graver normal modes of the Earth which are sensitive to density through self-gravitation effects induced in deformation.
  The present generation of density models has been constructed using linearized inversion techniques from earlier models, which ultimately relate back to models developed by Bullen and based in large part on physical arguments. A number of experiments in non-linear inversion have been conducted using the PREM reference model, with fixed velocity and attenuation, but with the density model constrained to lie within fixed bounds on both density and density gradient. A set of models is constructed from a uniform probability density within the bound and slope constraints. Each of the resultant density models is tested against the mass and moment of inertia of the Earth, and for successful models a comparison is made with observed normal mode frequencies. From the misfit properties of the ensemble of models the robustness of the density profile in different portions of the Earth can be assessed, which can help with the design of parametrization for future reference models. In both the lower mantle and the outer core it would be desirable to allow a more flexible representation than the single cubic polynomial employed in PREM.     

Viscosity profile of the lower mantle

Summary. We determine the variation of effective viscosity η across the lower mantle from models of the Gibb's free energy of activation G * and the adiabatic temperature profile. The variation of G * with depth is calculated using both an elastic strain energy model, in which G * is related to the seismic velocities, and a model which assumes G * is proportional to the melting temperature. The melting temperature is assumed to follow Lindemann's equation. The adiabatic temperature profile is calculated from a model for the density dependence of the Grüneisen parameter. Estimates of η depend on whether the lower mantle is a Newtonian or power law fluid. In the latter case separate estimates of η are obtained for flow with constant stress, constant strain rate, and constant strain energy dissipation rate. For G * based on the melting temperature, increases in η with depth range from a factor of about 100 for Newtonian deformation or power-law flow with constant stress to about 5 for non-Newtonian deformation with constant strain rate. For G * based on elastic defect energy, increases in η with depth range from a factor of about 1500 for Newtonian deformation or power-law flow with constant stress to about 10 for non-Newtonian deformation with constant strain rate. Among these models, only a non-Newtonian lower mantle convecting with constant strain rate or constant strain energy dissipation rate is consistent with recent estimates of mantle viscosity from post-glacial rebound and true polar wander data.     

汉水水系水环境中稀土元素的分布特征

系统探讨了汉水水系水相（原水、滤水、悬浮物）、沉积物相中8个稀土元素的含量水平、丰度模式、悬浮物含量对水中元素含量的影响及沉积物粒度对元素的富集与分散作用等，结果表明：Eu、Lu主要以溶解态存在于水相中，而Sm主要存在于悬浮物中；汉水水中稀土元素的含量基本在世界淡水的范围内；湖库悬浮物中稀土元素含量均低于江河悬浮物，悬浮物和细粒沉积物中稀土元素含量相近，序列也基本一致；粒度对汉水沉积物中稀土元素含量的影响不明显；地表径流对水中悬浮物含量和悬浮物中稀土元素含量均有一定影响，稀土元素在汉水悬浮物、沉积物中均有一定程度的富集现象；汉水各相中均以轻稀土为主，重稀土含量较少。     

"数字地球"与对地观测

在２１世纪到来之际,人类向“数字地球”这一地球信息科学新领域发起了挑战。这是在信息社会、知识经济、可持续发展时代背景下,由空间科学、信息科学、地球科学和环境科学的相互交融,在全球及区域尺度上的一次大整合、大聚焦。是面向２１世纪地球系统科学思维模式的开拓大跳跃。对地观测技术系统的蓬勃发展,是“数字地球”的不可缺少的基础。数字地球的发展,离不开对地观测技术系统的支撑。     

中国出口增加值的区域分布格局及其演变趋势

利用2002、2007和2010年中国非竞争型区域间投入产出表,对这3个年份中国八大区域出口增加值进行测算,揭示出口增加值的区域分布和经济贡献率格局,并探讨了格局演变的趋势特征和主要原因。结果显示：中国的出口增加值在规模、产业结构和经济贡献率指标上都存在东中西部的梯度差异;2002年以来中西部地区出口增加值的快速增长,在全国出口增加值中的占比由2002年的14.6%增长到2010年的23.2%,改变了其分布格局;在区域政策和要素成本变化的共同作用下,中部与西南地区在劳动与技术密集型产业的出口增加值增速加快,而东部和南部沿海地区在资源与劳动密集型产业的出口增加值增速放缓,推动了分布格局的演变。最后为区域出口增加值的提质增效提出了几点建议。     

On the distribution of anomalous mass within the Earth: forward models of the gravitational potential spectrum using ensembles of discrete mass elements

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We investigate forward models of the gravitational potential spectrum generated by ensembles of discrete sources of anomalous mass, having radial distributions with different statistical properties. Models with a random distribution of point source locations throughout the volume of the mantle produce spectra similar to that of the Earth only when the (absolute) source magnitudes increase strongly with depth, at least as d ^1.5. The effects of the geographic (latitude-longitude) distribution of source locations are generally unimportant in determining the general degree dependence of the potential spectrum. The dimensions of the sources are also of secondary importance, at least up to an angular diameter of about 40, i.e., continent-sized. Sources of this size confined to the upper mantle do not appear capable of producing the degree dependence of the observed geopotential spectrum; the low harmonics (2-4) in particular appear to require lower mantle sources of considerable strength. Further, at least some of these deep sources must be largely monopolar in nature, (i.e., uncompensated) due to the stronger depth attenuation of dipole (compensated) sources. Because topography on the core-mantle boundary must be either isostatically or dynamically compensated, it may contribute little strength to the observed potential spectrum.