Earthquake hazard assessment from the recent space and surface measurements of the Earth's gravity field

The distinctive nature of the structure of the Earth's gravity field over high seismicity areas, as observed in some limited scale studies, indicates that it is possible to use these associative patterns to outline areas of high seismicity or high earthquake hazard potential from a knowledge of the finer structure of the Earth's gravity field. The global scale investigation of such relationships as a function of the geophysical characteristics of various tectonic provinces, and the parameterisation of such relationships by hypocentral depth and earthquake intensity/energy data, become even more attractive because of the availability of (1) satellite-determined gravity models which provide global information on the long wavelength components of the gravity field, (2) satellite altimetry data which provide oceanwide information on the detailed geoidal structure, (3) surface gravity data which provide information on the short wavelength components in the areas of surface gravity coverage, and (4) bathymetric and topographic data which, though still somewhat limited in spite of their recent extensions of coverage, are available in more and more areas and provide information on the tectonic and morphological environments of an area to enable its gravity data conversion to some standard environments for direct comparisons of underlying structures. Additionally, the rapidly mounting geological and geophysical evidence of considerable intraplate tectonic activity, not so fashionable until recently, makes the study of these correlative patterns even more attractive and productive from a scientific viewpoint. This paper presents the major elements of the theoretical formulation for conducting such investigations.     

Continental ice sheets and the planetary radiation budget

The interaction between continential ice sheets and the planetary radiation budget is potentially important in climate-sensitivity studies. A simple ice-sheet model incorporated in an energybalance climate model provides a tool for studying this interaction in a quantitative way. Experiments in which the ice-sheet model is coupled step by step to the climate model show that ice sheets hardly affect the zonal mean radiation balance because the albedo feedback due to sea ice and snow cover is dominating. The model requires a 5% drop in the solar constant to create ice sheets of ice-age size.If the feedback between surface elevation and ice-mass balance is included (in a very crude way), the ice-sheet size (L, measured southward from 70°N) becomes much more sensitive to in insolation. For a range of normalized solar constants, roughly from 0.98 to 1.02, two stable solutions exist: L 0 and L 2000 km. This result demonstrates that the response of ice sheets to insolation variations is far from linear. It also stresses the need for explicit modeling of the ice-mass balance of ice sheets, particularly its dependence on surface elevation.     

藏东南地区复杂下垫面辐射收支特征分析

利用藏东南地区进行的地气交换观测数据, 分析了典型晴天和阴天不同下垫面辐射过程的特征及其差异. 结果表明: 藏东南地区典型晴天不同下垫面总辐射均呈现出明显的日变化规律, 典型阴天各下垫面总辐射日峰值与典型晴空天气下的总辐射日峰值差值不大, 日均值显著减小; 反射辐射日变化趋势与总辐射变化一致, 但变化曲线比总辐射离散, 阴天地表反射辐射受总辐射和下垫面的综合影响; 向上长波辐射日变化幅度和量值都大于向下长波辐射, 下垫面类型对向下长波辐射没有影响. 净辐射具有明显的日变化特征, 和总辐射的相位一致, 农田净辐射的日峰值和日均值最大.     

Life's a beach: lessons from the Earth's rarest sedimentary rocks

Ancient rockshore deposits are the rarest sedimentary rocks on Earth. Less than 200 examples span the planet's entire history, but they preserve important records of past environments, including sea-level changes and unusual fossil communities. The most celebrated example, dating from the earliest Jurassic, is found at Ogmore-by-Sea in South Wales. This article describes the history of environmental change at Ogmore, and why these rocks can help us to interpret the deposits of ancient rocky shores world-wide.     

Origin of the Earth's moon: Constraints from alkali volatile trace elements

Although the Moon is depleted in volatile elements compared to the Earth, these depletions are not in accord with simple volatility. For example, the $\text{Cs}\text{Rb}$ ratios of the Earth and Moon inferred from basalts are approximately one seventh and one half of the CI ratio, respectively. Volatility considerations alone predict that the lunar $\text{Cs}\text{Rb}$ ratio should be equal to or lower than the terrestrial ratio if the Moon was derived entirely from Earth mantle material. Thus hypotheses such as rotational fission which invoke derivation of lunar material entirely from the Earth's mantle may be excluded. The collisional ejection hypothesis of lunar origin requires at least 18% of lunar material to be derived from a projectile with dehydrated CI composition to match the lunar $\text{Cs}\text{Rb}$ ratio, and 25%–50% to match both the lunar $\text{Cs}\text{Rb}$ ratio and absolute concentrations of Cs and Rb. It remains to be demonstrated that this relatively large contribution of projectile material is consistent with other elemental abundances and element ratios in the Moon.     

Symmetry of the Earth's planetary relief

The order in structure of planetary relief is characterized by the following symmetrical attitudes of forms: antisymmetry of the north and south hemisphere (polar antisymmetry), underlined by availability of antianalogical forms; symmetry of cone in the Laurasian continental massif in the north hemisphere; symmetry of axis of the 4th order in the south hemisphere. In the West Pacific region the summation of private dissymetries of planetary relief structure occurs. The Earth's equatorial belt has a system of sinistral oroclines. Symmetrical peculiarities of planetary relief structure may allow us to suppose that the main process of the Earth's development during the Post-Gondwanian epoc (middle-Jurassic-Cenozoic period) was anisotropic expansion, mainly in the south hemisphere. Other tectonic processes, including lithospheric plate displacements, occur simultaneously with the normal process of the Earth's expansion.     

通过第一性原理预测内地核的成分与结构

内地核成分与结构的确定一直是地球深部研究的重要课题。目前地核的公认成分是铁和少量的镍。但由于地核密度低于纯粹的铁镍合金(固态内核2%～3%,液态外核6%～7%),其中必定掺杂有一定量的轻元素,其种类与浓度有待确定。除成分外,地核条件下铁的晶体结构也存在争议。根据地震学观测,声波沿地轴方向的传播速度比赤道平面方向快大约3%～4%。这意味着内地核是各向异性的;但在极端高压下,晶体结构中的原子应该按致密的密排六方结构(h.c.p)排列,而h.c.p结构对声波传输是高度各向同性的,这就需要确定地核条件下铁的晶体结构。根据第一性原理计算得到的高压下体系能量以及爱因斯坦谐振子模型,本项研究估算了给定结构的自由能以及掺杂轻元素后的影响。根据计算结果可以定性的分析得出,在高压OK下致密的h.c.p结构显然比疏松的体心立方(b.c.c)更稳定;而随着温度的升高,原子核的振动造成b.c.c结构的自由能比h.c.p结构下降得更快,因此在高温下b.c.c结构更稳定;掺杂轻元素后,这种优势变得更加明显,而3.6at.%的Si则恰好同时解释了2%～3%的密度缺失和b.c.c结构在内地核条件下的稳定性。因此我们建议内地核的基本结构与成分应为以体心立方结构存在的铁,掺杂约3.6at.%的硅元素,内地核温度至少在5500K以上。这一结论与其它更复杂的方法得到的结果一致。     

地幔中水的存在形式和含水量

水以含水变质矿物、无水硅酸盐矿物(橄榄石、辉石等)及其高压结构相(β橄榄石、γ橄榄石、钙钛矿相、方镁铁矿等)、高密度含水镁硅酸盐和熔体的形式存在于地幔各层圈中。根据各类玄武岩水含量推断出的上地幔源区的水含量,和由地幔岩主要矿物———橄榄石的水含量估算出的上地幔水含量(质量分数)很接近,在0.02%左右。以橄榄石和辉石高压相的水含量为依据,进行了过渡带和下地幔水含量的估算,其结果是:过渡带和下地幔上部的水含量(质量分数)为1.48%,下地幔下部水含量(质量分数)为0.21%。据此,计算出的地幔各层圈的总水量表明,地幔水的74%以上存在于过渡带和下地幔上部。将地幔总水量和现代海洋总水量之和作为地球总水量,计算出现代海洋总水量约占全球总水量(质量分数)的6.6%,这个结果与笔者根据地球的球粒陨石成分模型计算出的总水量(6%)十分接近。     

区域地球多圈层交互带调查探索研究

地球系统科学已成为国际地学研究的热点之一,也是目前解决复杂生态环境问题的主要途径。本文以冀东地区为例,将区域地质调查与地球多圈层交互带研究相结合,以1:5万水文地质调查为依托,构建出一套地球多圈层交互带生态地质调查与填图体系,为冀东地区农作物重金属离子超标、土地利用类型变化、矿山开采等一系列环境问题的解决提供地学建议。通过上述探索研究,提出区域地区地球多圈层交互带调查思路:以地球系统科学理论为指导,以区域生态环境问题为导向,通过开展地球多圈层交互带调查,完成地球多圈层交互带生态地质图,为生态环境问题的解决提供地学建议,为山水林田湖草海统一规划和管理提供科学依据。     

Grain structure of the Earth's inner core

The coarsening rate of an initial grain structure is calculated and compared to the inner core growth rate. An estimate of the present size of the grains in the centre of the core varies from 560 m to 12 km, depending on the value taken for the diffusion coefficient of iron in the core. Regardless of the hypotheses chosen, this size is homogeneous inside the inner core.     

Annual variations in the surface radiation budget and soil water and heat content in the Upper Yellow River area

Measurements taken between July 2006 to May 2007 at the Maqu station in the Upper Yellow River area were used to study the surface radiation budget and soil water and heat content in this area. These data revealed distinct seasonal variations in downward shortwave radiation, downward longwave radiation, upward longwave radiation and net radiation, with larger values in the summer than in winter because of solar altitudinal angle. The upward shortwave radiation factor is not obvious because of albedo (or snow). Surface albedo in the summer was lower than in the winter and was directly associated with soil moisture and solar altitudinal angle. The annual averaged albedo was 0.26. Soil heat flux, soil temperature and soil water content changed substantially with time and depth. The soil temperature gradient was positive from August to February and was related to the surface net radiation and the heat condition of the soil itself. There was a negative correlation between soil temperature gradient and net radiation, and the correlation coefficient achieved a significance level of 0.01. Because of frozen state of the soil, the maximum soil thermal conductivity value was 1.21 W m⁻¹°C⁻¹ in January 2007. In May 2007, soil thermal conductivity was 0.23 W m⁻¹°C⁻¹, which is the lowest value measured in the study, likely due to the fact that the soil was drier then than in other months. The soil thermal conductivity values for the four seasons were 0.27, 0.38, 0.55 and 0.83 W m⁻¹°C⁻¹, respectively.     

Observing the atmospheric wind from space

Among the basic variables that characterize the thermodynamic state of the atmosphere, wind is relatively poorly observed. Surface measurements by in situ sensors are numerous, but irregularly distributed over the globe. Upper level winds are characterized by radiosoundings that are reliable and accurate, but in a very limited number due to their expensive cost. They are complemented by wind measurements performed by commercial aircrafts, but these data are mostly acquired along the major flight routes at a cruising altitude of ～10 km. Radio sondes and aircrafts leave large gaps in the observation network that have been partly complemented for 10 years by an increasing amount of wind information derived from cloud tracking in satellite images, and more recently, surface winds by scatterometers. However, the observation capacity still suffers deficiencies as there is still no information in cloud-free parts of the atmosphere, and no complete vertical profiles except for the radiosoundings. They should be overcome with the launch in 2011 of the European satellite ADM-Aeolus, a space-based Doppler lidar currently under development at the European Space Agency.     

Observations of the Earth's atmosphere: Introductory remarks

The Earth is surrounded by a layer of relatively thin gas, the mass of which is mainly concentrated in the first kilometres. With an exponential decrease of the density of the atmosphere as a function of altitude, 99.9% of this mass is located in the first 50 km. In addition, the composition of major species is homogeneous up to about 85 km, contrarily to what happens beyond. This is the homosphere. This layer of atmosphere, considered in this special issue, is also that which we breathe and which we unfortunately often pollute. All this justifies considering it as of vital importance, in the most basic sense of the word. However, in studying it, it is not possible to ignore what is happening beyond, from where comes, in particular, solar radiation, just as we cannot ignore what happens below the continents and the oceans, where solar radiation is absorbed, diffused and re-emitted to the top by the Earth's surface as infrared radiation. We must therefore keep in mind what are the layers that surround the homosphere, the importance of observing them and also give some examples of possible interactions which may exist with the surrounding layers; these are the objectives of these introductory remarks. Another general consideration must be made here, concerning the problems, which have existed until the middle of the 20th century, of how to observe the atmosphere in situ at all the altitudes. However, since then, the development of engineering involving balloons, rockets, aircrafts and artificial satellites has revolutionized our knowledge of this observational atmosphere; this is the second message of these remarks.     

The Effect of the Earth's Rotation on Geotectonics

正 If we disregard the minor tectonic features, the world's principal mountain systems may be generalized and schematically represented in Fig. 1. This simplest pattern of geotectonics is very speculative. It leads us immediately to     

Limits of stress measurements in the Earth's crust

Summary Limits of Stress Measurements in the Earth's Crust. Accurate measurements of stress in the Earth's crust cannot be performed at deep levels with currently available recording procedures. The maximum stress recordable is about 100MPa, and the maximum depth 1000–1200 m.

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Zusammenfassung Grenzen der Bestimmbarkeit der Spannungen in der Erdkruste. In großen Tiefen kann mit derzeit verfügbaren Untersuchungsmethoden die tatsächliche Spannung in der Erdkruste nicht bestimmt werden. Die größte meßbare Spannung beträgt ungefähr 100 MPa, die größte Tiefe 1000–1200 m.

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Résumé Limites de la possibilité de la détermination des contraintes dans l'écorce terrestre. Il est impossible de faire des déterminations exactes des contraintes dans l'écorce terrestre en utilisant les méthodes courantes. La contrainte la plus grande qui peut être mesurée est à peu près 100 MPa et la profondeur maximale 1000–1200 m.

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A lecture delivered at the Joint General Assemblies of the IASPEI and IAVCEI in Durham, August 1977.

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With 4 Figures     

地核物质成分研究进展

系统介绍了地核的形成时间、地核的物理特性、化学成分和物质存在相态.利用W-Hf同位素系测年方法厘定地核与地幔分异的年龄是在地球形成的最初30 Ma.但是,内核的结晶年龄还是未知的.地核声波速度的各向异性可能是六面体紧密堆积(hcp)相铁的C轴方向沿地球轴线优选定向排列引起的.利用地球物理资料估算的地核密度与响应温压条件...