Wave propagation in physical models of micromorphic media     

Lothar Dresen  Jan Kozák  Aleš Špičák  Ludvík Waniek  Roman Teisseyre  Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1984,28(3):272-285

Summary The propagation of seismic waves in a micromorphic body, which is supposed to be one of the possible models of the medium in the earthquake focus, is studied by means of the two-dimensional ultrasonic model technique. The results obtained indicate that such a medium is characterized by distinct elastic anisotropy and by increased attenuation. The propagation velocity of longitudinal waves decreases and their amplitudes change considerably. The prevailing frequency of the waves passing through the micromorphic medium tends smoothly to one value which depends on the space distribution, orientation and dimensions of the elements characterizing such a medium. The obtained results are confronted with the theory of a micromorphic medium.

---

anmau uu u ¶rt;, n muu ¶rt; u ¶rt; ¶rt; a mu, uam nm ¶rt; ma ¶rt;uau. mam naam, m maa ¶rt;a muam n aumnu u n nu. m anmau n¶rt;u n¶rt; nuam, u anum¶rt; m. a¶rt;aa amma , n¶rt;u u ¶rt;, na mum ¶rt; uu, ma aa nmam an¶rt;u, anam u aau ¶rt;m, n¶rt;u m ¶rt;. mam auam mu u ¶rt;.

  相似文献   

Do some shallow earthquakes have a tensile source component?     

J. Šílený  A. R. Ritsema  I. Csikos  J. Kozák 《Pure and Applied Geophysics》1986,124(4-5):825-840

The laboratory tests carried out in studying shear and tensile seismogenic displacements occurring in compressed samples, led us to search for earthquakes with a tensile source component. To determine this component in the seismic focus, a special procedure based on the construction of radiation patterns of the combined shear-tensile type is introduced.The criteria for selecting the events produced by the combined source mechanism are listed, and their limitations are mentioned. From the seismic zones with good azimuthal distribution of stations in the world seismic network nine earthquakes which occurred in the 6-year period 1976–1981 were analyzed; for these events better agreement of the observed and theoretical patterns was found for the combined shear-tensile source mechanism than for the pure double-couple mechanism. However, the share of the tensile component was always, found to be relatively small, ranging from 1 to 13 percent of the shear component. The comparison of the two solutions (double-couple vs. combined shear/tensile) is based on the first onset signs statistics.The results obtained indicate that tensile fracturing does not play a substantial role in the total amount of released seismic energy; on the orther hand, it is expected to be more important in the creation and development of focal zone morphology from both the instantaneous and long-term point of view.  相似文献   

Refraction of elastic waves into a medium of lower velocity — Pseudospherical waves     

V. Červený  J. Kozák  I. Pšenčík 《Pure and Applied Geophysics》1971,92(1):115-132

Summary An irregular wave group (here called pseudospherical), the existence of which is connected with the velocity boundary at which the velocity decreases discontinuously, is investigated. A schlieren modelling device was chosen for a model investigation of this wave since it permits the investigation of wave fields inside the measured models. The model consisted of two layers of transparent gels, the source lay in the layer of higher velocity. The measurements have shown that an irregular wave in the layer of lower velocity exists only in a certain region along the boundary; its wave front has a spherical form and its intensity decreases rapidly with increasing distance of the source from the boundary. The wave always comes only after the regular refracted wave which conforms with the ray theory. These properties correspond to the properties of a wave first described byOtt [1]³) andBrekhovskikh [2]. In the conclusion of the present paper the possibilities of recording pseudospherical waves in seismology are outlined.  相似文献   

Laboratory investigations on fault plane induced tensile cracks     

Jan Kozák  Jan Šílený  Ludvík Waniek  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1981,25(4):332-342

Summary Tensile cracks induced by stress concentration around a fault plane in physical models under uniaxial load were analyzed. The results characterizing the decisive role of the fault plane inclination to the the stress direction are presented. Two stages of tensile crack life were determined, i.e. the first, seismoactive stage, accompanied by seismic energy release and the second aseismic one characterized by low velocity of crack propagation. Results obtained seem to be relevant to a better understanding of the character and regime of actual seismoactive faults.  相似文献   

Pictorial Series of the Manifestations of the Dynamics of the Earth: 2. Historical Images of World Volcanoes     

Kozák  Jan  Špičák  Aleš  Hanuš  Václav 《Studia Geophysica et Geodaetica》2001,45(4):445-456

Studia Geophysica et Geodaetica -  相似文献   

Zoosporic aquatic fungi growing on dead specimens of 29 freshwater crustacean species   总被引：1，自引：0，他引：1  

Bazyli Czeczuga  Mariola Koz&#x;owska  Anna Godlewska 《Limnologica》2002,32(2)

The authors investigated aquatic fungi growing on the carapaces of 29 species of dead crustaceans (13 species of Copepoda, 13 species of Cladocera and 3 species of Ostracoda) in the water from six limnological and trophical different water bodies (two springs, one river, one lake and two ponds). All of these waterbodies are strongly loaded. 146 species of aquatic fungi were found on the carapaces: 40 Chytridiomycetes, 1 Hyphochytriomycete and 105 Oomycetes. The most common fungus species were Karlingia chitinophila, Myzocytium microsporum, Myzocytium zoophthorum, Pythium acanthicum, Pythium butleri and Pythium myriotylum. Most zoosporic fungus species were observed on the specimens of Daphnia pulex (50 fungus species), Daphnia magna (48) and Cyclocypris laevis (44), fewest on Cyclops fuscus and Cyclops vicinus (each 10).The most fungi were growing in the water from River Supraśl (86), the fewest in the water from Pond Fosa (53). Cluster analysis of the investigated parameters carried out in water bodies during the experiment on zoosporic fungus species has revealed that in the water from springs and Pond Fosa the number of fungus species is closely associated with the concentration of sulphates, in water from River Supraśl and Lake Komosa with calcium and in the water from Pond Dojlidy with chlorides. Out of these 146 species, 21 are known as parasites or necrotrophs of fish. Some dead specimens of crustacean species are a new substrate for some fungus species.  相似文献   

Seismic events with non-shear component: I. Shallow earthquakes with a possible tensile source component     

Jan Kozák  Jan Šílený 《Pure and Applied Geophysics》1985,123(1):1-15

The concept of seismicity of fast tensile fracturing is introduced and supported by the results of shear and of combined shear and tensile displacements along a loaded stress concentrator. The seismicity of tensile fracturing is demonstrated by means of acoustic (elastic) signals obtained during tensile fracturing in physical models under load; the basic physical relations between the parameters characterizing the loaded medium, load conditions, shear and tensile displacements, and release of acoustic energy are presented. For determining the tensile-source component in earthquakes a procedure based on the construction of radiation patterns is suggested and submitted for discussion. The criteria for selecting earthquakes with possible shear-tensile source mechanisms are listed and discussed. The existence of such a combined seismic source is sought in two shallow earthquakes which occurred in southern Iran in March 1977. In general, the paper should be regarded as a proposal to utilize the radiation characteristics of a seismic source—with all their insufficiencies—as a quick and simple tool for seeking combined shear and tensile mechanisms of seismic energy release.  相似文献   

Structural dynamic analysis of the epicentral zone of the Ilin-Tas earthquake (Feb 14, 2013, Ms = 6.9)     

L. P. Imaeva  B. M. Koz’min  V. S. Imaev  K. G. Mackey 《Journal of Seismology》2015,19(2):341-353

  相似文献   

Distribution of secondary minerals in crusts developed on sandstone exposures          下载免费PDF全文

Zofia Alexandrowicz  Mariola Marszałek  Grzegorz Rzepa 《地球表面变化过程与地形》2014,39(3):320-335

Previous research on rock weathering crusts has revealed their large variability depending on the type of host rocks and development of weathering processes. The composition of crusts developed on natural sandstone exposures is less documented in the literature in comparison to those developed on architectonic stones. In both cases, previous research has focused mainly on the progress of salt weathering. This study considers the surfaces of sandstone tors in the Polish Outer Carpathians. The exposed parts of the rocks in this area are often covered by crust, which is up to several centimetres thick, and differs from the internal part in colour and composition. The crusts were characterized using light and electron microscopy, X‐ray diffractometry, thermal analyses, Mössbauer spectroscopy, bulk chemical analyses and sequential chemical extractions. Porosity was estimated by digital image processing. The following two hardened zones were observed: (1) thin (up to 30 µm), black, external layer, rich in carbon and composed of opal‐type silica, covered in places by sulphate incrustations and numerous spherical particles of anthropogenic origin; (2) thicker (up to several millimetres), internal part composed of a set of laminae of variable colouration, enriched in iron (oxyhydr)oxides (goethite and hematite) in comparison to the rock interior. Development of the crust results from silicon and iron redistribution during the sandstone alteration. The chief source of silica is hydrolysis of aluminosilicates, whilst that of iron is decomposition of aluminosilicates, carbonates and sulphides. Hematite is probably a result of goethite transformation. However, air pollutants may play an important role in the formation of sulphates. Silica and iron compounds affect the properties of the rock, hardening the surface and lowering porosity by formation of secondary cement. Crystallization of sulphate salts, in turn, may contribute to mechanical disintegration of the rock. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

The Messina-Reggio earthquake of December 28, 1908     

J. M. Carcione  J. T. Kozák 《Studia Geophysica et Geodaetica》2008,52(4):661-672

  相似文献