50th Birthday of professor a Zátopek     

Jiři Vaněk 《Studia Geophysica et Geodaetica》1957,1(1):196-196

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INFLUENCE OF NUMBER AND SPACING OF SENSORS ON THE EFFECTIVENESS OF SEISMIC ARRAYS*     

R. A. HARTENBERGER  R. G. Van NOSTRAND 《Geophysical Prospecting》1972,20(4):771-784

Ideally, geophones would be placed in a noiseless environment, in which case there would be no reason to resort to arrays of geophones. If the noise is such that an array is required, the objective of the array is to enhance the signal-to-noise ratio and thus to maximize the intelligence that can be derived from a given signal. The design of the array will be a function of the signal characteristics, of the direction and velocity of the noise in the bandpass of the signal, and of the site geology. It has been demonstrated previously that in a practical sense the optimum array processing is represented by precise beam forming, by which we mean simple time-delay and summation. Increasing the number N of sensors within a given area decreases the inter-element spacing and may increase the coherency between noise samples at adjacent sensors, thus yielding poorer results compared to √N improvement one expects to get if the noise is uncorrelated. Increasing the number of sensors by proportionately increasing the area is liable to result in signal deterioration, also yielding an unfavorable comparison to √N improvement in signal-to-noise. These two effects, together with economical factors, combine to limit the number of sensors that can be used. Although the data on which our conclusions are reached were drawn from earthquake seismology, the principles involved are equally applicable to exploration seismology and to other geophysical measurements in which arrays of sensors are required.  相似文献   

Hinsdalite and corkite: Indicator minerals in central Africa     

L. Van Wambeke 《Mineralium Deposita》1971,6(2):130-132

Hinsdalite and corkite have been found in the Kivu Province, Rep. of Congo (Kinshasa) by using the combined X-ray diffraction-fluorescence method. The X-ray data as well as the optical properties and chemical composition of both minerals are described. Hinsdalite and corkite could be interesting as indicator minerals for the search of ore deposits. They indicate the existence of a new mineralization in the Kivu Province.

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Résumé De l'hinsdalite et de la corkite ont été trouvées dans la Province du Kivu, Rép. du Congo (Kinshasa) en utilisant la méthode combinée diffraction-fluorescence X. Les données des rayons X, les propriétés optiques et la composition chimique de ces deux minéraux sont décrites. L'hinsdalite et la corkite pourraient étre intéressants comme indicateurs minéraux pour la recherche de gisements. En effet, ces minéraux indiquent l'existence d'une nouvelle minéralisation dans la Province du Kivu.

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An attempt to determine long-periodic variations in the drift of horizontal pendulums     

Petr Vaníček  Reviewer L. Skalský 《Studia Geophysica et Geodaetica》1971,15(3-4):416-420

Résumé On donne les résultats de l'analyse de la dérive des pendules horizontaux de la station Píbram-Bezové Hory au cours des années 1927–1938. Différemment aux résultats publiés déjà antérieurement[2], on a tout d'abord séparé par la méthode des moindres carrés la dérive linéaire et le terme à période de durée d'un an exactement et ce n'est que le reste qu'on a analysé par la méthode de l'analyse spectrale spéciale[4, 6]. On a trouvé dans les deux éléments une période de 222, respectivement 223 jours, non considérée jusqu'alors et ne pouvant pas être interprétée jusqu'à présent du point de vue physique. Les autres résultats sont en bon accord avec ceux reçus à l'origine. On peut conclure de la comparaison des phases des composantes annuelles des pendules horizontaux et du mouvement du pôle[5] que les deux événements sont du même origine.  相似文献   

Revised amplitude curves of seismic body waves for the region of south-eastern europe     

Jiří Vaněk 《Studia Geophysica et Geodaetica》1969,13(2):173-179

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The Uranium-lead isotopic dating of South African acid lavas     

Van Niekerk  C. B.  Burger  A. J. 《Bulletin of Volcanology》1968,32(3):481-498

Bulletin of Volcanology -  相似文献   

A second occurrence of non-metamict davidite     

L. Van Wambeke 《Mineralium Deposita》1968,3(2):178-181

A second occurrence of non-metamict davidite has been found in the Kirumba syenitic massif, Kivu, Rep. of Congo (Kinshasa). Its properties are described. Its geochemical data support the hypothesis of a genetic relationship between the Kirumba massif and the alkaline complex with carbonatites of Lueshe.

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Résumé Une seconde occurrence de davidite non-metamicte a été trouvée dans le massif syénitique des Kirumbas, Kivu, Rép. du Congo (Kinshasa). Ses propriétés sont décrites. Les données géochimiques sont en faveur d'une relation génétique entre le massif des Kirumbas et le complexe alcalin à carbonatites de Lueshe.

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A numerical diffusion model for continuous releases     

C. J. P. Van Buijtenen  J. Holland  D. Van Leeuwen 《Boundary-Layer Meteorology》1973,5(3):275-283

The purpose of this study was to develop a diffusion model for a continuous point source which takes into account the increase of wind speed with height, and to compare this model with short-range diffusion experiments. The main problem was to find a good expression for the vertical diffusion coefficient. It turned out that good agreement between theory and experiment could only be obtained by introducing a settling speed W for the tracer combined with a conventional expression for the vertical diffusion (K(Z) = K ₀Z^1−p). An empirical relation was found between K ₀ and τ _vU and between W and bar σ _vU².  相似文献   

Geodynamic models for the Alpine type of orogeny (Test-case II: the Alps in central Europe)     

R.W. Van Bemmelen 《Tectonophysics》1973,18(1-2)

Two modern geodynamic models on the Alps are tested: plate tectonics (mechanical effects of colliding lithospheric mega-units), and mantle diapirism (mechanical and geochemical effects of ultra-lowvelocity bodies, rising from the low-velocity layer or asthenosphere). Verification occurs by means of comparing the expectations of these models (their ‘prognoses’) with the great wealth of available ‘diagnostic’ facts on the geology and geophysics of the Alps. It appears that the picture of the Alpine structural evolution, drafted by plate tectonics, is inadequate to describe the observed reality, whereas the idea of mantle diapirism, combined with crustal corrosion (geochemical oceanization) and gravity tectonics, provides a functionally correct model, that logically and coherently explains the entire Alpine cycle of orogeny.In the concluding remarks comparisons are made with the formation of island arcs in the western Pacific, the origin of the basin-and-range topography and volcanicity along the eastern margin of the Pacific, as well as the Sunda arc of Indonesia.  相似文献   

Results of deep seismic soundings along international profile VII in Czechoslovakia and poland     

Břetislav Beránek  Milica Mayerová  Milada Zounková  Alexander Guterch  Rufin Materzok  Jan Pajchel  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1973,17(3):205-217

Summary The paper deals with the results of DSS measurements along international profile VII, carried out by Czechoslovak and Polish geophysicists in 1970 – 71. The profile situation is shown in Fig. 1. By 1971 part of the profile in the region of the Bohemian Massif between points 1 and 3 and in Poland between points 5 and 7 had been surveyed (Fig. 2). The seismograms were used to construct the travel-time curves of the fundamental types of waves P^K, P^M, P_n (Fig. 4). The mean velocities were computed from the travel-time curves of the reflected waves (P^M and P^K) and the refracted waves (P_g). Isolines of the mean velocities could be constructed for the region of the Bohemian Massif (Fig. 6). The velocity data found were used for the depth interpretation of the travel-time curves of the principal types of waves and to construct a seismic section (Fig. 8). In the region of the Pre-Sudeten block the thickness of the crust was found to be 34–37 km, and in the Sudeten it increased to 40 km. Towards the south the thickness of the crust gradually reduces to 30 km in the system of the Luice faults. In the Bohemian Cretaceous the thickness of the crust is about 30 km. Further to the south, in the region of the Moldanubicum, the thickness of the Earth's crust increases rapidly, and at the southern border of the Central Bohemian pluton it reaches values of about 42 km.  相似文献