Trajectory of fault-plane-induced tensile crack in relation to the primary stress field     

Jan Šílený  Reviewer K. Pěč 《Studia Geophysica et Geodaetica》1982,26(4):352-360

Summary The predetermination of the trajectory of a tensile crack induced at the tip of a stress-free fault plane (open slit, in two dimensional approximation) was investigated. Both the primary field of the tensile component of principal stress and the primary field of the strain energy density factor were computed and compared with the trajectory of the subsequent tensile crack. It was found that it is not the field of the strain energy density factor, but the field of the tensile component of principal stress which determines the trajectory of the tensile crack. Moreover, this field is responsible for the trajectory of the tensile crack not only in its seismoactive phase of its development, but also in the following aseismic stage characterized by slow stable growth.  相似文献   

Dynamics of a system of admixture particles in a hydrodynamic field,its states and stability     

Jiří Horák  Reviewer J. Narrátil 《Studia Geophysica et Geodaetica》1982,26(1):81-92

Summary An analysis of the equation for geodetic distance is presented, based on the condition of integrability of the equation for the covariant derivative of the velocity of an admixture particle in a fluid and on the assumption that the motion is taking place in a compact varieta along trajectories close to geodesics. A pattern of state is thus obtained in the neighbourhood of equilibirum state in the appropriate space of states, and we decide about its stability in the sense of the Lyapunovian theory of stability of the quiescent condition. The conditions of integrability are also considered with regard to the metric in conformal Euclidean (conformally flat) form.  相似文献   

A method of reducing the disturbing effects in gamma — Spectrometric measurements of rock radioactivity     

Milan Krešl  Věra Vaňková  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1982,26(1):66-73

Summary The long-termed stability of the NTA 1024 Gamma spectrometer was investigated. In order to reduce the influence of the instability of the linear amplifier, a method of mathematical transformation of the spectrum was introduced.  相似文献   

Modelling of the sensing system of a vibrational magnetometer by digital computer     

Tomáš Zelinka  Pavel Hejda  Josef Bochníček  Reviewer F. Janák 《Studia Geophysica et Geodaetica》1982,26(3):272-280

Summary An analytico-numerical computation of the transfer function of the sensing system of a vibrational magnetometer is presented. In discussing the results, the properties of the method are pointed out and a proposal for the sensing system is made with regard to the required sensitivity of the instrument.  相似文献   

Investigation of the stochastic properties of anomalous geophysical potential fields defined at points of the surface of an ellipsoid     

Ludmila Kubáčková  Reviewer J. Anděl 《Studia Geophysica et Geodaetica》1981,25(3):211-223

Summary Using a general model, constructed for random fields defined on a Lyapunov surface, the stochastic properties of fields defined at points of the surface of a tri-axial rotational ellipsoid are investigated within the correlation theory of these fields.  相似文献   

Computation of ray integrals and ray amplitudes in radially symmetric media     

Jaromír Janský  Vlastislav Červený  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1981,25(3):288-292

Summary A new approximation of the velocity-depth distribution in radially symmetric media is suggested. This approximation guarantees the continuity of velocity and its first and second derivatives, and does not generate false low-velocity layers. It removes false anomalies from the amplitude-distance curve and considerably increases its stability. The evaluation of ray integrals and ray amplitudes using this velocity-depth approximation does not require the computation of any transcendental function and is, therefore, very fast. Numerical examples are presented.  相似文献   

On the problem of equal area block on a sphere     

Karel Klíma  Miloš Pick  Zdeněk Pros  Reviewer M. Burša 《Studia Geophysica et Geodaetica》1981,25(1):24-35

Summary A new untraditional way of dividing the sphere surface into an arbitrary number of equal area blocks by means of a spiral is proposed and its statistical properties are analysed.  相似文献   

Understanding Vesuvius magmatic processes: evidence from primitive silicate-melt inclusions in medieval scoria clinopyroxenes (Terzigno Formation)     

A. Lima  H. E. Belkin  K. Török 《Mineralogy and Petrology》1999,65(3-4):185-206

Summary Microthermometric investigations of silicate-melt inclusions and electron microprobe analyses were conducted on experimentally homogenized silicate-melt inclusions and on the host clinopyroxenes from 4 scoria samples of different layers from the Mt. Somma-Vesuvius medieval eruption (Formazione di Terzigno, 893 A.D.). The temperature of homogenization, considered the minimum trapping temperature, ranges from 1190 to 1260 ± 5 °C for all clinopyroxene-hosted silicate melt inclusions.The major and minor-element compositional trends shown by Terzigno scoria and matrix glass chemical analysis are largely compatible with fractional crystallization of clinopyroxene and Fe-Ti oxides. Sulfur contents of the homogenized silicate-melt inclusions in clinopyroxene phenocrysts compared with that in the host scoria show that S has been significantly degassed in the erupted products; whereas, Cl has about the same abundance in the inclusions and in host scoria. Fluorine is low (infrequently up to 800 ppm) in the silicate-melt inclusions compared to 2400 ppm in the bulk scoria.Electron microprobe analyses of silicate-melt inclusions show that they have primitive magma compositions (Mg# = 75-91). The composition of the host clinopyroxene phenocrysts varies from typical plinian-related (Mg#85) to non plinian related (Mg#85). The mixed source of the host clinopyroxenes and primitive nature of the silicate-melt inclusions implies that these phenocrysts, in part, may be residual and/or have a polygenetic origin. The similar variation trends of major and minor-elements between homogenized silicate-melt inclusions from the Terzigno scoria, and silicate-melt inclusions in olivine and diopside phenocrysts from plinian eruptions (Marianelli et al., 1995) suggest that the trapped inclusions represent melts similar to those that supplied the plinian and sub-plinian magma chambers. These geochemical characteristics suggest that the Vesuvius magmatic system retained a vestige of the most recent plinian event.

---

Primitive Silikatschmelz-Einschlüsse in Klinopyroxenen aus mittelalterlichen Schlaken der Terzigno Formation — Ein Beitrag zum besseren Verständnis der magmatischen Prozesse des Vesuvs

Zusammenfassung Mikrothermometrische Untersuchungen von Silikatschmelz-Einschlussen und EMS Analysen wurden an experimentell homogenisierten Silikatschmelz-Einschlussen und an Klinopyroxenen von vier Schlackenproben durchgeführt. Die Proben stammen aus verschiedenen Lagen der mittelalterlichen Mt. Somma-Vesuv Eruption (Terzigno Formation, 893 n. chr.). Die Homogenisierungstemperaturen, sie werden als die minimalen Einschlußtemperaturen interpretiert, reichen von 1190–1260±5 °C.Die Trends der Haupt- and Spurenelemente der Terzigno Schlacken and des MatrixGlases sind weitgehend mit fraktionierter Kristallisation von Klinopyroxen und Fe-TiOxiden kompatibel. Der Vergleich der Schwefel-Gehalte der homogenisierten Einschlüsse in den Klinopyroxen-Phdnokristallen mit denen der Schlacken zeigt, daß beträchtliche Mengen an Schwefel in den Eruptionsprodukten durch Entgasung verlorengingen. Chlor hingegen zeigt in etwa die gleiche Verteilung in den Einschlüssen und in der Wirtsschlacke. Die Fluorgehalte in den Einschlüssen (selten bis zu 800 ppm) Bind im Vergleich zu den Schlacken (2400 ppm) niedrig.EMS-Analysen der Silikatschmelz-Einschlüsse belegen eine primitive Schmelzzusammensetzung (#Mg = 75–91). Die Zusammensetzung der Klinopyroxen-Phänokristalle variiert zwischen plinianischen Typen (#Mg 85) und nicht-plinianischen (#Mg85). Die heterogene Quelle der Klinpyroxene and die primitive Natur der Einschlüsse lassen vermuten, daß die Phänokristalle residualen und/oder polygenetischen Ursprungs sind. Ähnliche Haupt- und Spurenelementtrends der untersuchten Einschlüsse mit jenen von Einschlüssen in Olivin- und Diopsid-Phänokristallen aus plinianischen Eruptionen (Marianelli et al., 1995) legen die Vermutung nahe, daß die Einschlüsse ähnliche Schmelzen repräsentieren, wie jene, die die plinianischen und die sub-plinianischen Magmenkammern versorgt haben. Diese geochemischen Charakteristika belegen, daß das magmatische System des Vesuvs eine Spur des jüngsten plinianischen Ereignisses bewahrt hat.

---

---

With 11 Figures  相似文献   

Temporal Variations in Sea Surface Topography and Dynamics of the Earth's Inertia Ellipsoid     

Burša  Milan  Kouba  Jan  Raděj  Karel  True  Scott A.  Vatrt  Viliam  Vojtíšková  Marie 《Studia Geophysica et Geodaetica》1999,43(1):7-19

Temporal variations in the nine elements of the Earth's inertia ellipsoid due to sea surface topography dynamics were derived from TOPEX/POSEIDON altimeter data 1993 - 1996. The variations amount to about 10 mm in the position of the center of the Earth's inertia ellipsoid (E _i ), 0.15' in the polar axis direction of E _i and to about 0.0003 in the denominator of its polar flattening. The approach used is based on the temporal variations of distortions computed by means of the geopotential model EGM96 which is used as reference.  相似文献   

Combinations of Satellite Crossovers to Study Orbit and Residual Errors in Altimetry     

Jaroslav Klokočník  Carl A. Wagner 《Celestial Mechanics and Dynamical Astronomy》1999,74(4):231-242

We define combinations of dual‐ and single‐satellite crossover differences to isolate both stationary orbit‐geopotential and non‐geopotential errors in altimetry data. Specifically two types of combinations are found useful. While no combination of differences can resolve the full radial error of single or paired satellites, an approximation of the mean or geographically correlated error of the generally dominant lower orbit of a pair can be found from one kind (substitutions). (The variable part of the error is always available from the single‐satellite crossover differences.) A second useful combination type is found to yield no geopotential orbit error (zeros): uniquely, these can reveal errors in altimetry from imperfect media corrections as well as oceanographic changes in sealevel. The later circumstance is particularly important when the missions for a pair of satellites are disparate in time. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献