Vertical movements of the Earth's crust on the continents

Vertical oscillating movements of the Earth's crust on continents have occurred and are occurring everywhere on the Earth's surface, continuously throughout the entire geological history of the Earth. This provides grounds to consider them as the basic type of tectonic movements, which form the general background of the tectogenetic process, on which locally, and only at separate moments of time, other tectonic movements and deformations appear.According to the time of occurrence, the vertical movements are divided into recent, young, modern, and ancient. In compliance with this subdivision, different methods are applied to define and study the movements. The major characteristic of the vertical movements is their rhythm, or periodic change in sign of movement, which caused them to be calledoscillating. Rhythms of movements are of several orders. The largest rhythms, which comprise tectonic cycles, are manifested on a global scale; smaller rhythms have a local distribution. It is significant that, in the beginning and in the end of each tectonic cycle, an increase of intensity and contrast of movements is observed, no matter in which region or regime, whether stable or mobile, it occurs.     

Hydrogeological indications of recent movements of the earth's crust

Hydrogeologic indications of recent movements of the Earth's crust in two regions of North Tian-Shan have been studied. Comparison of ground-water level changes and variations of recent vertical movements according to benchmarks located near a well demonstrates their good correlation. The ground-water level varies out of phase with the direction of vertical movements. A correlation between level variation and seismic regime has been observed up to a well, located in a near-fault zone. In the region of the Kochkorskaya Depression, well observations show that against a background of constant increasing of level, sharp decays are observed. The latter can be connected with creep displacements. Hydrogeologic observations, together with periodic levelling enable us to study recent movements of the Earth's crust in detail.     

A new version of the map of recent vertical crustal movements in the Carpatho-Balkan region based on the collocation method

The paper is concerned with the problem of adequate mapping of resulting discrete values of the movement velocity as a field. The authors used a statistical method (collocation) to represent measurement results for the Carpatho-Balkan region as a field of recent crustal movement velocity. The collocation method gives a possibility of avoiding a strong influence that the available geomorphological and geological knowledge of the area and individual notions of map-makers have on the drawing of isolines of velocity movements. The new version of the map of recent vertical movements in the Carpatho-Balkan region shows some notable differences from the 1979 version.     

New investigations or recent vertical movements in the Carpatho-Balkan region

Recent work concerning the investigation of vertical movements in the Carpatho-Balkan Region is reported, based on the “Explanatory Text to the Map of Recent Vertical Movements in the Carpatho-Balkan Region”.For this investigation, the following countries supplied information: Bulgaria, Czechoslovakia, GDR, Hungary, Poland, Romania, USSR, Austria, and Italy. The activities were coordinated by the Hungarian Geodetic Service. Hungary undertook the task of collecting the data, their preparation for adjustment, and the adjustment of the investigation network, as well as the compilation and publication of the map of vertical movement. The authors present the algorithm of the rigorous adjustment: the height differences of the second leveling have been adjusted jointly with the velocities derived from the first and second levelings.In this paper the applied geodetic and oceanographic data, as well as the main character of the investigation network are presented. The interpretation of the adjustment is outlined.The map of Recent Vertical Movements in the Carpatho-Balkan Region (CBR) is printed at the scale of 1:1,000,000.In general, it is claimed that due to the new methods of investigation, the new CBR map of vertical movements provides a better tool to help with further investigations.     

A rectified map of recent vertical surface movements in the West Carpathians in Slovakia

The first-order relevelling network in Slovakia (International Relevelling Program) was supplemented by second-order relevelling lines measured at the time of the International Relevelling Program (1973–1978) or after its completions, in order to gain more detailed information on the movement activity of the West Carpathians in Slovakia. Mathematical evaluation of relevelling results allowed of drawing a map of recent vertical movements in the region at the scale of 1:1,000,000.The Czechoslovak Uniform Levelling Network of 1947–1962 and the 2nd Czechoslovak Relevelling Network of 1973–1983 constitute the geodetic basis of the map. The relative annual movement velocities, as related to the Initial Fundamental Benchmark Pitelová near Žiar nad Hronom (approximately in the centre of Slovakia) are represented by isolines at intervals of 0.5 mm per year.An analysis of the map 1952–1977 indicates an overall subsidence of lowland regions with respect to the mountanous regions of the West Carpathiams. Central Carpathian morphostructures feature uplifts, with some regions appearing to be stable. Over the entire period under study, the maximal values of vertical movements were + 1.0 mm/year (uplifts) and -4.0 mm (subsidences), the total range being 5 mm/year.     

一种通过共轭地震确定地壳的内摩擦特性的方法

应用国内外24个具有"X"形或"L"形（不完整的"X"形）共轭破裂特征的地震资料,以及云南鲁甸、盈江两次共轭破裂地震的详细重定位数据,运用库仑破坏准则揭示的脆性破裂的共轭破裂角与介质的内摩擦系数之间的关系,测定与计算了地震共轭角与地壳的内摩擦系数,探讨了库仑破坏准则与安德逊破裂理论应用于宏观尺度破裂即天然地震问题.结果表明,在国际、国内不同地区不同年代的多次共轭破裂地震中,共轭角与内摩擦系数的优势分布分别为65°~75°与0.27~0.47.在同一地区或相近地区发生的地震,其共轭角与内摩擦系数在数值上也相近.库仑破坏准则与破裂的安德逊理论,不但适用于实验室的小样本岩石破裂实验结果,而且适用于宏观尺度破裂即天然地震.通过共轭角的测定,可以确定地壳的内摩擦系数,是一种增进对地壳的内摩擦特性的认识的简易、直接的方法.     

A new map of recent movements of the West Carpathians

ma mam m n, a uum am mua ¶rt;uu ana¶rt; anam. am n a a u¶rt; m um u n u mmu n¶rt;u ¶rt;uu. ¶rt; u n mam a n muu amu amu mam nm uu u n m¶rt;u mau am ¶rt;uu nmu, ma u n u¶rt;au ¶rt;uauu . am unam m ¶rt; a , u u¶rt;uu u mu namu nu nmuauu n u u, ammu uu¶rt;muu u a a.     

A model for attenuation and scattering in the Earth's crust

The mechanisms contributing to the attenuation of earthquake ground motion in the distance range of 10 to 200 km are studied with the aid of laboratory data, coda wavesRg attenuation, strong motion attenuation measurements in the northeast United States and Canada, and theoretical models. The frequency range 1–10 Hz has been studied. The relative contributions to attenuation of anelasticity of crustal rocks (constantQ), fluid flow and scattering are evaluated. Scattering is found to be strong with an albedoB ₀=0.8–0.9 and a scattering extinction length of 17–32 km. The albedo is defined as the ratio of the total extinction length to the scattering extinction length. TheRg results indicate thatQ increases with depth in the upper kilometer or two of the crust, at least in New England. CodaQ appears to be equivalent to intrinsic (anelastic)Q and indicates that thisQ increases with frequency asQ=Q _o f ⁿ , wheren is in the range of 0.2–0.9. The intrinsic attenuation in the crust can be explained by a high constantQ (500Q _o2000) and a frequency dependent mechanism most likely due to fluid effects in rocks and cracks. A fluid-flow attenuation model gives a frequency dependence (QQ _o f ^0.5) similar to those determined from the analysis of coda waves of regional seismograms.Q is low near the surface and high in the body of the crust.     

Early crust on top of the Earth's core

In an effort to resolve the current conflict between geochemical requirements for an apparently isolated mantle reservoir and recent geophysical evidence for whole-mantle convection, we investigate the possibility that the region above the core-mantle boundary, termed D″, serves as an early-isolated, rare-gas- and incompatible-element-bearing reservoir, and we propose a mechanism for its formation that is a likely outcome of Earth accretion models. In these models, the most cataclysmic event in Earth history, the moon-forming giant impact on the proto-Earth of a Mars-size planet (perhaps as early as 4540 Ma ago) was followed by accretion of smaller bodies long afterwards (until ∼3900 Ma). Some collisions probably triggered melting, metal segregation and degassing. However, the small bodies, fragments, particles, dust, including those of chondrite-like composition, existed on near-earth orbits, were irradiated by intense solar wind, and finally fell on an early-formed, incompatible-element-enriched basaltic crust without causing extensive melting. The respective regions of the crust, loaded with chondrite-like debris, were therefore significantly enriched in iron. When this mixed material was subducted, the bulk density of the subducted lithosphere exceeded that of the bulk silicate mantle, which had already lost its metallic iron to the core. Segregation of this denser material at the base of the mantle was facilitated by the high temperatures at the core-mantle boundary, which greatly reduce the viscosity, as was quantitatively modelled by Christensen and Hofmann (Christensen, U.R., Hofmann, A.W., 1994. Segregation of subducted oceanic-crust in the convecting mantle. J. Geophys. Res.-Solid Earth 99 (B10), 19867–19884). Assuming a basalt/chondrite mass ratio of about 4/1, we obtain a density contrast of ∼7%, which would stabilize the subducted material between the metal core and silicate mantle.Mass balance considerations and preliminary results of geochemical modelling of the above scenario (similar to that performed by Tolstikhin and Marty [Tolstikhin, I.N., Marty, B., 1998. The evolution of terrestrial volatiles, A view from helium, neon, argon and nitrogen isotope modeling. Chem. Geol. 147, 27–52]) show the potential geochemical importance of D″. (1) Modelling of Pu–U–I–Xe isotope systematics predicts formation of this reservoir early in Earth history, ∼100 Ma after formation of the Solar system. (2) The total amount of heat-generating U, Th, K (and other highly incompatible elements) in D″ exceeds 20% of the Earth inventory, and a similar portion of terrestrial heat is being transferred from the core + D″ into the base of the overlying convecting mantle. (3) D″ is enriched in solar implanted rare gases because the small (re)-accreting debris with high surface/mass ratios will have been subjected to intense radiation by the early sun. (4) Rare gases diffuse from D″ into the overlying mantle and are then transferred into upwelling plumes, which originate above D″. In addition, small amounts of D″ material may be entrained by the mantle convective flow as was recently discussed by Schott et al. [Schott, B., Yuen, D.A., Braun, A., 2002. The influences of composition and temperature-dependent rheology in thermal-chemical convection on entrainment of the D″ layer. Physics Earth Planet. Inter. 129, 43–65]. From the rare-gas modelling it follows that initially (∼4500 Ma ago) D″ could have been more massive by a factor of ∼1.2 than at present (about 2 × 10²⁶ g). The present-day mass flux from D″ into the convecting mantle is estimated to be ≤0.05 × 10¹⁶ g year⁻¹, a factor of ∼100 less than the rate of ridge magmatism. This small contribution of D″ material makes it difficult to trace fingerprints of D″ even using such sensitive tracers as Pb isotope ratios. (5) The density contrast that stabilizes D″ is maintained by its higher intrinsic density due to the iron-rich chondrite-like component. Subduction of this material, its entrainment by convective mantle flow and mixing could also account for the preservation of the chondritic relative abundances of siderophile elements in the mantle. If D″ is partially molten, the density contrast may be caused by a high-density melt fraction.     

地壳磁异常的全球模型

从全球磁场减去地核主磁场和变化磁场及其感应磁场后,就得到岩石圈磁场,又称地壳磁场,或地磁异常.地壳磁场是地磁场的重要组成部分,对导航、通信、地球物理勘探等有重要意义.本文简要综述近年来在地壳磁场基本信息获取方面取得的重大进展,特别是Oersted、CHAMP等卫星磁侧的最新成果,介绍在此基础上建立的全球磁异常模型,展望地壳磁场研究的发展趋势和应用前景.     

Maps of recent vertical crustal movements in Romania: Similarities and differences

A new map of recent crustal vertical movements (RCVM) in Romania, on the basis of high-precision geodetical measurements by the repeated levelling method, had become necessary firstly as a consequence of the great seismic event of March 4, 1977 with foci under the Vrancea Region (the most important seismic zone in the country) and secondly because many years had passed since the previous edition.Certainly, there are similitudes and differences between the two editions, and the authors will try to put these into evidence and explain them.The general view of the major geological units of Romania in both maps is the same: the mountain regions being zones of more or less continuous uplift, the plains showing subsidence movements and the plateau regions presenting a relative stability. Some modifications became apparent owing to the improvement of the national geodetical network on which the repeated levelling measurements were performed and following the choice of the Harbour of Constanţa as the fundamental point.     

Recent movements of the earth's crust

Summary It has been shown that it is necessary to combine several methods to be able to describe and explain recent movements of the Earth's crust.Presented at the XV^th General Assembly of the IUGG, Moscow 1971.     

The relationship of recent vertical movements to the morphostructural pattern of the Kazakh shield

The geodetic data on recent vertical crustal movements within the Kazakh shields is in good correlation with its development in the Holocene (according to a study of juvenile river terraces); they point to gradual transition of the shield to the platform morphostructures of Western Siberia and a contrasting joining with the Central Asia orogenic belt. Small gradients of recent vertical movements dominate the shield. Moderate gradients are typical of local structures, whereas increased and extremely high gradients belong to active deep fault zones.     

Seismotectonic model of the upper part of the Earth's crust of Czechoslovakia

Summary A correlation of the earthquake occurrence on the territory of Czechoslovakia and in its close neighbourhood with the data on the neotectonic and geomorphological development of the respective area, the recent movements of the Earth's crust, the courses of photolineations and on the geophysical fields enabled the fundamental structural blocks in the upper part of the Earth's crust to be singled out. The contact zones established between the above blocks exhibit increased long-term movement tendencies particularly in the Neoid period. A seismotectonic model of the upper part of the Earth's crust of Czechoslovakia, compiled with the use of the data mentioned above, is described.

---

u m uu mu a mumuu auu u mmu ¶rt;au n mmu,uu, ¶rt;uu , u nmu u uuuu n nua ¶rt;um mm u amu . a a ¶rt; muu au a¶rt;am amau ¶rt; ¶rt;uu, u¶rt; nu¶rt;. m n¶rt;aaa mmua ¶rt; amu aa a au¶rt;uauu n, nu¶rt;u a ua mumuu, u a u u n¶rt;uu au.

     

Induction in the Earth's crust: Observational methods on land and sea

During the last twenty years, the measurement of the Earth's electromagnetic field has been greatly improved. Old devices, such as suspended magnet variometers or the inductive sensors, are now up to date, thanks to the use of negative feedback techniques. Very sensitive instruments, like the superconducting quantum interference device (SQUID) are now available for geophysical applications. The extensive use of large arrays of magnetometers has permitted the study of the distribution of telluric flow inside the Earth's crust and the delineation of large, deep conductivity anomalies. We also have a better knowledge of the distribution of the resistivity at depth, even under the ocean bottom. But we are still very far from understanding how the telluric currents are induced in the Earth, especially at very low frequencies.

---

Résumé Depuis vingt ans la mesure du champ électromagnétique naturel s'est beaucoup améliorée. D'anciens instruments comme les variomètres à aimant suspendu ou les capteurs inductifs ont été remis en honneur grâce à l'utilisation de techniques nouvelles, comme la contre-réaction de champ. D'autres appareils, extrêmement sensibles, tels que les SQUID (superconducting quantum interference device) sont maintenant disponibles pour des applications géophysiques. L'usage intensif de réseaux de magnétomètres a permis d'étudier la distribution des courants telluriques en profondeur et de mettre en évidence d'importantes anomalies de conductivité. Nous avons aussi une meilleure connaissance de la répartition de la résistivité à grande profondeur y compris sous les océans. Mais nous restons très ignorants des mécanismes qui régissent l'induction des courants telluriques à l'échelle de la terre entière, particulièrement aux très basses fréquences.

     

地面扰动重力垂直梯度的确定

鉴于扰动重力垂直梯度在大地测量和物探中有重要作用,在未直接测量的情况下,对如何由地面重力异常及地形数据求取扰动垂直梯度进行了研究和分析,认为在被研点附近要求重力点分布密集,且精度不低于1×10-6ms-2;对中央区域积分奇异性问题也作了讨论;此外,扰动重力垂直梯度如何在大地测量和地球物理中进一步得到应用,以及为何用扰动重力垂直梯度代替重力异常垂直梯度也给予了简明的论述.     

利用重力/GPS联合观测数据计算地壳垂向构造应力的新方法

本文提出一种基于重力/GPS联合观测数据计算垂向构造应力的新方法.计算步骤如下:(1) 通过重力/GPS联合观测数据计算布格重力异常;(2) 依据布格重力异常数据推算莫霍面深度;(3) 依据GPS观测数据,通过均衡理论计算均衡面深度;(4) 依据莫霍面与均衡面之间剩余物质(壳幔物质密度差)所承受的附加浮力,计算地壳承载的垂向构造应力.本文利用上述构造应力新算法,计算了巴颜喀拉块体东边界及周边地区垂向构造应力分布,发现龙泉山断裂带以东地区垂向构造应力基本为零,龙泉山断裂带与龙门山断裂带之间地区垂向构造应力为正值,巴颜喀拉地块东部垂向构造应力为负值.鲜水河断裂带东南段周边蓄积了-40~-50 MPa的垂向构造应力,且梯度变化剧烈;松潘高原蓄积的垂向构造应力大约为-10~-20 MPa,相对较小.     

An experiment with joint mapping of the vertical velocity and its horizontal gradient in the study of recent tectonic movements

An experiment is described dealing with the detailed mapping of the vertical velocity V of recent crustal movements in the central Danubian riverside region of the Moesian platform in Northern Bulgaria. The error in V being significant here, the problem of statistical control on the reliability of the initial data and results of such studies is investigated; this question is also relevant for other platform regions in Eastern and Central Europe. With the aim of assessing the significance of a movement, the sampling distribution of V is used. The problem is reduced to a checking of a standard statistical hypothesis and to a probabilistic characterization of V. In order to estimate the statistical significance of the relative velocity δV between neighbouring benchmarks, the distribution of the module G of the horizontal gradient of V is studied. An agreement between the sampling distribution obtained and the theoretical Weibull distribution is established. A sufficiently high probability P>86% is determined for the significance of δV in this region and an optimal interval of the isobases is suggested. The experiment itself embraces three variant solutions: independent mapping of V, independent mapping of G, and mapping of V with respect to G. The analysis and comparison of the results obtained demonstrate the high efficiency of the third solution.