非洲、澳洲、南美洲的连环拼合与成因探讨     

李维渡 《地球物理学进展》2001,16(1):56-61

通过对非洲、澳大利亚、南美洲彼此之间的大陆架边界线相似的概率分析，指出巧合是不可能的，地球在过去几十亿年间一定发生了大规模的膨胀。  相似文献   

Image resolution and evaluation of genetic hypotheses for planetary landscapes     

James R. Zimbelman 《Geomorphology》2001,37(3-4)

The spatial resolution of image data tends to constrain the horizontal length scale of genetic hypotheses that are addressable by those data. No ‘simple’ formula exists when image resolution is sufficient to test a given geomorphic process, which is dependent on what characteristics are diagnostic of the particular process. Genetic hypotheses should be formulated along the lines of the “multiple working hypotheses” concept as described in a classic paper by Chamberlin [J. Geol. 5 (1897) 837]. An essential element of a viable working hypothesis is a clear indication of the characteristics predicted by, or a consequence of, the hypothesis. An untestable hypothesis is not an effective working hypothesis. The history of the study of lunar sinuous rilles is outlined as an illustration of the influence of image resolution and the formulation of genetic hypotheses on the subsequent advancement of understanding of the problem. Sinuous rilles on Venus and Mars, and controversial sinuous ridges on Mars are also reviewed. In the lunar case, the three-order-of-magnitude improvement in spatial resolution provided by Lunar Orbiter photographs over Earth-based telescopic photographs did not result in definitive examination and elimination of published hypotheses for the formation of sinuous rilles. Topographic data obtained from cartographically controlled Apollo orbital photographs, along with important observations and samples obtained by the astronauts on the lunar surface, did test and exclude several hypotheses. The formulation of a genetic hypothesis, including testable consequences of that hypothesis, is a greater determinant of its ultimate utility to the scientific community than is the image resolution available at any given time.  相似文献   

Rodinia超大陆构造演化研究的新进展和主要目标   总被引：13，自引：1，他引：13  

徐备 《地质科技情报》2001,20(1):15-19

概略评述了1997年以来国际上有关Rodinia超大陆构造演化问题的研究成果，并提出今后工作的主要目标。Rodinia超大陆的聚合造山发生在1300－1000Ma，基本形式表现为早期弧一陆碰撞和晚期陆－陆碰撞，并在1000－900Ma继以伸展作用。Rodinia超大陆的裂解发生于830Ma之后，但其过程具有明显的时，空分布不均一性，地幔柱可能是导致超大陆裂解的主要机制，大火成岩省”是地幔柱发育的关键性标志，已经初步证实裂解过程影响地球大气圈和水圈中二氧化碳的循环，进而改变晚前寒武纪的全球气候，控制生物圈的兴衰和岩石圈表层的碳酸盐，铁，锰和磷等沉积，这些现象可用“雪球化地球”（Snowball Earth)模式概括。  相似文献   

El Niño Impact on Polar Motion Prediction Errors     

Kosek  W.  McCarthy  D.D.  Luzum  B.J. 《Studia Geophysica et Geodaetica》2001,45(4):347-361

The polar motion prediction is computed as a least-squares extrapolation of the polar motion data. The least-squares model consists of a Chandler circle with constant or variable amplitude, annual and semiannual ellipses, and a bias. The model with constant amplitude of the Chandler oscillation is fit to the last three years of polar motion data and the model with variable amplitude of the Chandler oscillation is fit to the whole time series ranging from 1973.0 to 2001.1. The variable amplitude of the Chandler oscillation is modeled from the envelope of the Chandler oscillation filtered by the Fourier transform band pass filter from the long-term IERS EOPC01 polar motion series. The accuracy of the polar motion prediction depends mostly on the phase variation of the annual oscillation, which is treated as a constant in the least-squares adjustment. There were two significant changes of the annual oscillation phase of the order of 30° before the two El Niño events in 1982/83 and 1997/98.  相似文献   

Low Electrical Resistivity And Seismic Velocity At The Base Of The Upper Crust As Indicator Of Rheologically Weak Layer     

L. Vanyan  B. Tezkan  N. Palshin 《Surveys in Geophysics》2001,22(2):131-154

Conductivity models were compiled in two geological provinces with thinsediments. The first province is the margin of the Precambrian East EuropeanPlatform. The second one is the Phanerozoic Rhenish Massif as a part of CentralGermany Hercinicum. In both provinces, a conducting layer was revealed at thebase of the upper crust by the magnetotelluric soundings. Its depth is around10 km in the East European Platform and around 15 km in the Rhenish Massif.The conductance of the layer reaches a few tens of Siemens in the first provinceand is almost an order of magnitude greater in the second one.A good correlation between the conductor and a seismic wave-guide (low-velocityzone) exists at the base of the upper crust. Simultaneous decrease of both electricalresistivity and seismic velocity, suggests an increase of porosity and permeability inpresence of saline water. The depth of rheological weak layer in the PhanerozoicRhenish Massif corresponds to the commonly accepted depth of the thermallyinduced brittle/ductile transition. Contrary similar layer in the Precambrian EasternEuropean Platform is much shallower than the thermally induced transition. Somenew mechanism should be considered.  相似文献   

关于当代地球科学发展趋势的点滴认识     

吴凤鸣 《吉林地质》2001,20(4):4-6,32

面对资源、环境、人口、地质灾害等人类的生产、生活乃至生存的严峻危机，需要我们掌握地球内部的客观规律，不断更新和寻找地球科学理论和新的思维方式，掌握地球科学发展趋势，以协调好人与自然、人地关系及社会经济和可持续发展理论，造福于人类。  相似文献   

球面小波分析技术及在全球重力模型中的应用     

许惠平  刘万崧  R.H.N.Haagmans  A.J.Th.deBrnoue 《物探与化探》2001,25(1):8-13

在介绍球面小波理论的基础上,推导和比较了几种球面小波,分析了最新地球重力模型-EGM96,以此为依据,把球面小波多分辨分析用于计算全球自由空气异常及重力大地水准面,并对处理结果做出解释。  相似文献   

A Reliability Based Expert System for Assessment and Mitigation of Landslides Hazard Under Seismic Loading     

Al-Homoud  Azm S.  Tahtamoni  Wisam W. 《Natural Hazards》2001,24(1):13-51

Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides.  相似文献   

Detection of seepage paths in earth dams using self-potential and electrical resistivity methods   总被引：7，自引：0，他引：7  

T. V. Panthulu  C. Krishnaiah  J. M. Shirke 《Engineering Geology》2001,59(3-4):281-295

Earth and rockfill dams are designed to operate under steady state seepage. Anomalous seepage may be a threat to the integrity of the structure. In spite of advances made in the fields of geotechnical engineering, it is not possible to have 100% leak-proof structure. Any excessive and unplanned seepage may lead to the failure of the dam, especially in unconsolidated or fractured terrains. Geophysical methods play an important role in mapping seepage paths and monitoring the changes of the seepage with time, enabling to plan technically and economically worthwhile remedial measures. In the present paper, utilisation of electrical methods for delineation of seepage zones at two of the four Saddle dams of the Som-Kamla-Amba project, Rajasthan State, India; which is founded on heterogeneous rock mass, is discussed. Electrical resistivity method was used to delineate zones favourable for seepage, whereas, self-potential (SP) method was used to delineate the seepage paths. SP measurements have shown negative anomaly of the order of 10–20 mV in amplitude, indicating low seepage, coinciding with the seepage measurements made by the project authorities.  相似文献   

体应变观测中的气压干扰机制和排除方法的研究   总被引：7，自引：0，他引：7  

张凌空  何世海  刘北顺 《地震》1996,(2)

建立体应变理论气压干扰模型,通过实际观测资料研究了气压对体应变月变和日变的干扰过程,探讨消除干扰的方法,且和水位资料作了对比分析。  相似文献