Spectral-element simulations of global seismic wave propagation—II. Three-dimensional models, oceans, rotation and self-gravitation     

Dimitri Komatitsch  Jeroen Tromp 《Geophysical Journal International》2002,150(1):303-318

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Tensorial formulation of the wave equation for modelling curved interfaces   总被引：1，自引：0，他引：1  

Dimitri Komatitsch  Fabien Coutel  Peter Mora 《Geophysical Journal International》1996,127(1):156-168

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Risk Assessment of Soil Compaction in the Walloon Region in Belgium   总被引：1，自引：0，他引：1  

Dimitri D’Or  Marie-France Destain 《Mathematical Geosciences》2016,48(1):89-103

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Uniform half-plane elastodynamic problems by an approximate boundary element method     

Dionyssia-Pinelopi N. Kontoni  Dimitri E. Beskos 《Soil Dynamics and Earthquake Engineering》1987,6(4):227-238

In this paper the applicability of an approximate Boundary Element Method to uniform half-plane elastodynamic problems is investigated. This method employs the concept of images to construct approximate fundamental solutions for the half-plane and does not require any half-plane surface discretization. The method is formulated in the frequency domain for the case of harmonic disturbances or the Laplace transform domain for the case of transient disturbances. In the latter case a numerical inversion of the transformed solution is necessary to obtain the time domain response. The proposed method can be used as an alternative to boundary element methods that either utilize the infinite plane fundamental solution and thus require a half-plane surface discretization, or employ the exact half-plane fundamental solution, which even though leads to no surface discretization, is of a very lengthy and complicated form. Two characteristics numerical examples are used to illustrate the proposed method and study its advantages and disadvantages.  相似文献   

Contribution au probleme de la compensation des reseaux de triangulation     

Dimitri G. Vlachos 《Journal of Geodesy》1970,44(3):213-223

Résumé Dans cette étude on expose une adaptation de la méthode des directions —pour la compensation d’un réseau de triangulation—aux possibilités de l’ordinateur électronique. On présente les formules par lesquelles on calcule les coefficients des inconnues dans les équations de condition (équations aux angles et équations aux c?tés) et on dresse leur matrice. Ensuite on traite de la formation de la matrice des coefficients des équations normales et son inversion, qui fournit les quantités corrélatives de Lagrange. Enfin, après avoir déterminé les corrections à apporter aux directions observées, on calcule l’erreur moyenne quadratique d’une observation isolée et l’erreur moyenne de chacune des directions compensées.

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Summary In this study, an adaptation to the computers’ possibilities, regarding the method of directions, is disclosed in order to realise the adjustment of triangulation nets. The computing formulae of the coefficients of the unknown quantities in the condition equations and the creation of their matrix are given herebelow. The treatment leading towards the construction of the matrix of normal equations and its inversion, that furnishes Lagrange’s quantities, follows. After the computation of the corrections applied on the observed directions, the mean error of a single observation and the mean error of every adjusted direction are determined. The study is executed in such a way that it can be included in only one programme for automatic computation.

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Calculation of the solar chromospheric Lα profile allowing for partial redistribution effects     

R. W. Milkey  Dimitri Mihalas 《Solar physics》1973,32(2):361-363

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From subduction to transform motion: a seabeam survey of the Hellenic trench system     

Xavier Le Pichon  Jacques Angelier  Jean Aubouin  Nicolas Lyberis  Serge Monti  Vincent Renard  Henri Got  Ken Hsu¨  Yossi Mart  Jean Mascle  Drummond Matthews  Dimitri Mitropoulos  Pandelis Tsoflias  Georges Chronis 《Earth and Planetary Science Letters》1979,44(3):441-450

Preliminary results of a multi-narrow beam survey of the Hellenic trench system, in the Eastern Mediterranean, are presented. The southwestern Ionian branch is divided in small basins, partly filled with Pleistocene sediments. The morphology suggests that the basins are deformed by a compressional stress acting roughly perpendicularly to the trench along N50°E. This direction is the direction of the regional slip vector of the shallow thrust-type earthquakes. The structure of the southeastern Pliny-Strabo branch is quite different. Narrow en-e´chelon slots, oriented N40°E, have been mapped within the main troughs oriented N60°E. The regional earthquake slip vector is also oriented along N40°E. We conclude that the Hellenic trench system is an active subduction system, dominated by thrust along the Ionian branch and by transform motion along the Pliny-Strabo branch.  相似文献   

Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry     

Karina Marshall-Bowman  Dimitri A. Sverjensky  Robert M. Hazen 《Geochimica et cosmochimica acta》2010,74(20):5852-5861

The abiotic polymerization of amino acids may have been important for the origin of life, as peptides may have been components of the first self-replicating systems. Though amino acid concentrations in the primitive oceans may have been too dilute for significant oligomerization to occur, mineral surface adsorption may have provided a concentration mechanism. As unactivated amino acid polymerization is thermodynamically unfavorable and kinetically slow in aqueous solution, we studied mainly the reverse reaction of polymer degradation to measure the impact of mineral surface catalysis on peptide bonds.Aqueous glycine (G), diglycine (GG), diketopiperazine (DKP), and triglycine (GGG) were reacted with minerals (calcite, hematite, montmorillonite, pyrite, rutile, or amorphous silica) in the presence of 0.05 M, pH 8.1, KHCO₃ buffer and 0.1 M NaCl as background electrolyte in a thermostatted oven at 25, 50 or 70 °C. Below 70 °C, reaction kinetics were too sluggish to detect catalytic activity over amenable laboratory time-scales. Minerals were not found to have measurable effects on the degradation or elongation of G, GG or DKP at 70 °C in solution. At 70 °C pyrite was the most catalytic mineral with detectible effects on the degradation of GGG, although several others also displayed catalytic behavior. GGG degraded ∼1.5-4 times faster in the presence of pyrite than in control reactions, depending on the ratio of solution concentration to mineral surface area. The rate of pyrite catalysis of GGG hydrolysis was found to be saturable, suggesting the presence of discrete catalytic sites on the mineral surface. The mineral-catalyzed degradation of GGG appears to occur via a GGG → DKP + G mechanism, rather than via GGG → GG + G, as in solution-phase reactions. These results are compatible with many previous findings and suggest that minerals may have assisted in peptide synthesis in certain geological settings, specifically by speeding the approach to equilibrium in environments where amino acids were already highly concentrated, but that minerals may not significantly alter the expected solution-phase equilibria. Thus the abiotic synthesis of long peptides may have required activating agents, dry heating at higher temperatures, or some form of phase separation.  相似文献   

Geological controls on submarine groundwater discharge in Long Bay,South Carolina (USA)     

Richard Viso  Clay McCoy  Paul Gayes  Dimitri Quafisi 《Continental Shelf Research》2010,30(3-4):335-341

A combination of geophysical methods including continuous electrical resistivity and high-resolution Chirp sub-bottom profiling were utilized to characterize geologic controls on pore fluid salinity in the nearshore of Long Bay, SC. Resistivity values ranged from less than 1 Ω m to greater than 40 Ω m throughout the bay. Areas of elevated electrical resistivity suggest the influence of relatively fresher water on pore water composition. Geophysical evidence alone does not eliminate all ambiguity associated with lithological and porosity variations that may also contribute to electrical structure of shallow marine sediments. The anomalous field is of sufficient magnitude that lithological variation alone does not control the spatial distribution of elevated electrical resistivity zones. Geographical distribution of electrical anomalies and structures interpreted from nearby sub-bottom profiles indicates abrupt changes in shallow geologic units control preferential pathways for discharge of fresh water into the marine environment. Shore parallel resistivity profiles show dramatic decreases in magnitude with increasing distance from shore, suggesting a significant portion of the terrestrially driven fresh SGD in Long Bay is occurring via the surficial aquifer within a few hundred meters of shore.  相似文献   

A surface complexation model for sulfate and selenate on iron oxides consistent with spectroscopic and theoretical molecular evidence     

Keisuke Fukushi  Dimitri A. Sverjensky 《Geochimica et cosmochimica acta》2007,71(1):1-24

Sulfate and selenate adsorption on iron oxides are important reactions in natural systems under a very wide range of pH values, ionic strengths, and electrolyte compositions. Under such conditions, spectroscopic and theoretical calculations have demonstrated the potential importance of a variety of surface species. Understanding the variations in the surface speciation of these oxyanions is fundamental to prediction of their partitioning between minerals and aqueous solutions. In the present study, published experimental spectroscopic and theoretical molecular evidence of the identity of sulfate/selenate surface species are integrated with a surface complexation model consistent with a wide variety of experimental adsorption, surface titration, and proton coadsorption data to define the surface speciation of sulfate and selenate on iron oxides under a wide range of conditions. The analysis was carried out with the extended triple layer model (ETLM) taking into account the electrostatics of water dipole desorption during ligand exchange reactions. On seven out of eight goethites studied, sulfate and selenate surface reactions can be represented by the formation of a monodentate-mononuclear inner-sphere and a bidentate-binuclear outer-sphere (or H-bonded) species according to