The fifth order geomagnetic multipole: The duotrigintupole     

Denis E. Winch 《Pure and Applied Geophysics》1967,68(1):90-102

Summary The notion of a dipole is generalized to the case of the fifth order spherical harmonic coefficients of the geomagnetic potential. The corresponding five axes and fifth order multipole strength are computed for ten epochs in the interval 1845 to 1965.  相似文献   

Lunar behaviour of boron contrasted with the terrestrial boron cycle     

Denis M. Shaw 《Meteoritics & planetary science》1995,30(2):199-208

Abstract— Fifty-eight lunar rocks have been analysed by prompt gamma neutron activation for B, Gd and Sm. The data were interpreted together with published analyses for Li and other elements. The behaviour of B in lunar rocks is virtually identical to that of Sm, Gd, Li and the other incompatible LIL (Large Ion Lithophile) and HFS (High Field Strength) elements, collectively known as the KREEP component. To a first approximation, the distribution of B concentrations in all lunar rocks can be described as a two-component mixture of KREEP, with ～32 ppm, and B-free mare basalts and anorthositic rocks. The lunar B abundance, estimated from correlations with other KREEP elements, is ～0.14 ppm. Alpha-track images of the analysed lunar rocks were made from thin sections specially prepared to avoid contamination from terrestrial B. They provided surprising evidence that the distributions of B and Li within individual rocks fall into four categories: (1) substitution in mineral structures; (2) in irregular minute particles, disseminated through the rock with no apparent connection with mineralogy; (3) as aggregate properties of rock fragments, acquired prior to assembly in a breccia; and, (4) as aggregate properties of a breccia matrix, distinct from unaffected clasts. Only category (1) is encountered in terrestrial rocks. Categories (2), (3) and (4) become progressively more important as the abundance of KREEP components increases, and it is concluded that the alpha-track images probably show the localisation of not only B and Li but all the KREEP elements. In terrestrial rocks, such textures could be understood in terms of successive episodes of permeation by solutions followed by brecciation, then cementation. It is difficult to adapt such a mechanism to a dry Moon, with brecciation imposed by impact melting. The linear correlation of lunar B and Gd contrasts strongly with the relationship seen in terrestrial rocks, where the presence of water creates a terrestrial B cycle quite different from that of Gd and other lunar incompatible elements.  相似文献   

Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2     

Toshifumi Yanagisawa  Yasushi Muraki  Yutaka Matsubara  Fumio Abe  Kimiaki Masuda  Sachiyo Noda  Takahiro Sumi  Yuji Kato  Mitsuaki Fujimoto  Shuji Sato  Ian Bond  Nicholas Rattenbury  Philip Yock  Pam Kilmartin  John Hearnshaw  Micheal Reid  Denis Sullivan  Brian Carter  Richard Dodd  Garry Nankivell  Noiman Rumsey  Morihiro Honda  Maki Sekiguchi  Masanori Yoshizawa  Takashi Nakamura  Humitaka Sato  Seiji Kabe  Makoto Kobayashi  Yoshiyuki Watase  Jun Jugaku  Toshiharu Saito  Barbel Koribalsky 《Experimental Astronomy》2000,10(4):519-535

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.  相似文献   

Steady- and transient-state inversion in hydrogeology by successive flux estimation     

Philippe Pasquier  Denis Marcotte 《Advances in water resources》2006,29(12):1934-1952

A calibration method to solve the groundwater inverse problem under steady- and transient-state conditions is presented. The method compares kriged and numerical head field gradients to modify hydraulic conductivity without the use of non-linear optimization techniques. The process is repeated iteratively until a close match with piezometric data is reached. The approach includes a damping factor to avoid divergence and oscillation of the solution in areas of low hydraulic gradient and a weighting factor to account for temporal head variation in transient simulations. The efficiency of the method in terms of computing time and calibration results is demonstrated with a synthetic field. It is shown that the proposed method provides parameter fields that reproduce both hydraulic conductivity and piezometric data in few forward model solutions. Stochastic numerical experiments are conducted to evaluate the sensitivity of the method to the damping function and to the head field estimation errors.  相似文献   

Seasonal fluctuations in the deep central equatorial Atlantic Ocean: a data–model comparison     

Virginie Thierry  Herlé Mercier  Anne Marie Treguier 《Ocean Dynamics》2006,56(5-6):581-593

Low-frequency current fluctuations in the deep central equatorial Atlantic are analyzed using current meter measurements recorded from November 1992 to November 1994. Current meters were located at about 14°W of longitude and 1° of latitude on both sides of the equator between 1,700 m depth and the ocean bottom. At all sampling depths, the velocity fluctuations are dominantly zonal and symmetrical with respect to the equator. At 1,700 and 2,000 m, the flow is dominated by annual period fluctuations, at 3,000 m, the velocity field amplitude presents a minimum, and at 3,750 and 3,950 m, the flow is modulated by annual and semiannual period variability. The annual signal exhibits an apparent upward phase propagation. When considering the phase and the amplitude of the seasonal fluctuations, the data compare well with the outputs of a realistic numerical simulation of the Atlantic Ocean. Together with a previous analysis of the model simulations, this supports the idea that the observed annual fluctuations are due to wind-forced vertically propagating Kelvin and Rossby waves. Data and model do not provide deciding evidences of the presence of semiannual equatorial waves deeper than 3,500 m depth in the central equatorial Atlantic Ocean.  相似文献   

郯庐断裂带(安徽段)及邻区的动力学分析与区域构造演化   总被引：11，自引：3，他引：11       下载免费PDF全文

侯明金  朱光  Jacques Mercier  Pierre Vergély  王永敏 《地质科学》2007,42(2):362-381

依据区域构造层次划分,采用构造筛分法,层层深入,层层筛分,确定发生于各个不同时代地层/岩层内的断裂活动的同期及叠加的应力场特征。综合所有的同期应力场特征及辅以叠加的应力场特征来验证,从而确定了一个连续的、完整的断裂活动的应力场演化序列;结合区域构造变形特征分析,阐明郯庐断裂带(安徽段)的构造演化。应力场分析显示:晚三叠-早侏罗世应力场为北北西—南南东或近南北向挤压,属古特提斯构造域,断裂发生同造山走滑;早白垩世早期,应力场为北西—南东向挤压,断裂发生左行走滑运动,中国东部处于西环太平洋构造域;早白垩世晚期—古新世(始新世),区域发生北西—南东向伸展作用,断裂处于伸展断陷作用阶段;新生代,受区域上近东西向的挤压作用影响,断裂发生挤压逆冲兼右行走滑作用。  相似文献   

TL age-estimates for the Middle Palaeolithic layers at Theopetra cave (Greece)     

Helene Valladas  Norbert Mercier  Laurence Froget  Jean-Louis Joron  Jean-Louis Reyss  Panajotis Karkanas  Eleni Panagopoulou  Nina Kyparissi-Apostolika 《Quaternary Geochronology》2007,2(1-4):303-308

The lowest stratigraphic unit of Theopetra cave (Greece) contains a Middle Palaeolithic sequence radiocarbon dated to between 46 and 35 ka BP; at the limit of this dating method. The upper part of this sequence has yielded late Middle Palaeolithic lithic assemblages containing several early Upper Palaeolithic artifacts. To get more precise dates for the human occupation of the cave, burnt flint specimens from these Middle Palaeolithic layers were dated by thermoluminescence. The dates obtained are coherent and indicate that the first human occupation of the cave took place at the end of isotopic stage 6 or more probably at the beginning of stage 5, much earlier than previously proposed. In the light of this new evidence, it is reasonable to assume that: (a) Theopetra contains the oldest dated Middle Palaeolithic deposits of Greece and (b) that the assemblages first interpreted as “Transitional Middle/Upper Palaeolithic” industries may be the result of post-depositional mixing of cultural material.  相似文献   

On the interest and the limits of using combined ESR/U-series model in the case of very late uranium uptake     

C. Falgures  J.-J. Bahain  J.-M. Dolo  N. Mercier  H. Valladas 《Quaternary Geochronology》2007,2(1-4):403-408

Before ESR/U-series models were applied to ungulate teeth, it is generally assumed that calculated ages are close to the “real” ages when they range between the values obtained with the EU and LU models. When the samples show signs of uranium-leaching, a realistic mathematical modelling of the age is not possible. On the other hand, some samples have undergone a very late U-uptake “affecting” directly the U-series ages and rendering the calculated ages younger.

We present results obtained on two open-air sites, which show the limits of such combined models in the case of late uranium incorporation. For the Middle Pleistocene site of Isernia la Pineta (Italy), the ESR dates are expected to fall within the limits imposed by the Ar–Ar results. The other site, the Lower Palaeolithic deposits of Ambrona (Spain), yielded two sets of samples: some at the top of the sequence with uranium uptake ranging between EU and LU limits and thus giving a good idea of the “real” age of the site; others at the base displaying a very late U-uptake, which render an age determination difficult.  相似文献   

The M_L 5.3 Épagny (French Alps) earthquake of 1996 July 15: a long-awaited event on the Vuache Fault     

François Thouvenot  Julien Fréchet  Paul Tapponnier  Jean-Charles Thomas  Benoît Le Brun  Gilles Ménard  Robin Lacassin  Liliane Jenatton  Jean-Robert Grasso  Olivier Coutant  Anne Paul  & Denis Hatzfeld 《Geophysical Journal International》1998,135(3):876-892

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Une méthode globale d'estimation des températures des réservoirs alimentant les sources thermales. Exemple du Massif Central Français     

Gil Michard  Christian Fouillac  Daniel Grimaud  Jérôme Denis 《Geochimica et cosmochimica acta》1981,45(7):1199-1207

A chemical model based on the equilibrium of water with quartz, albite, adularia, calcite, kaolinite or illite, and chlorite can explain the chemical composition of the main groups of hot springs in Massif Central. Temperature is the principal variable for determining this composition. Model temperatures generally agree with those given by classical cation geothermometers (t ? 135–150° C for Vichy. La Bourboule. Evaux and Châteauneuf; t ? 175–180° C for Chaudes Aigues and Saint Nectaire). The model fails to represent the composition of Mont Dore waters: the high temperatures given by classical geothermometers are considered doubtful.  相似文献