Temperature and frequency dependence of electric parameters of igneous rocks

Zusammenfassung Es wurde die Temperatur- und Frequenzabhängigkeit der elektrischen Leitfähigkeit der Eruptionsgesteine verfolgt. Mit Ausnahme der Serpentinit-Proben richtet sich die elektrische Leitfähigkeit im ganzen Temperaturintervall nach dem Exponentialgesetz der Abhängigkeit von der Temperatur. Im Frequenzintervall 10²–10⁵ Hz kommt es zu einer starken Dispersion der elektrischen Leitfähigkeit, die mit dem Wachstum der Temperatur sinkt und bei hohen Temperaturen von ca.1000–1050°C praktisch schwindet. Die dielektrische Konstante als Funktion des Frequenzlogarithmus sinkt scharf. Bei tiefen Temperaturen (bis300–400°C) wurde ein Gebiet sehr schwacher Dipol-Polarisation beobachtet.     

Regionally metamorphosed greisens at Cetoraz,the Bohemian-Moravian Heights (Českomoravská vrchovina), Czechoslovakia

Investigation of the greisen occurrence at Cetoraz, Bohemian-Moravian Heights, which underwent a regional metamorphism, has shown that the main greisen assemblages are stable under the conditions of regional metamorphism, as long as they do not attain the sillimanite-almandine-orthoclase subfacies, when muscovite disappears. The ore minerals are also stable. In the mineralogy of the greisens, the regional metamorphism manifests itself only by the presence of subordinate minerals typical of regional metamorphism, such as sillimanite or spinel.     

Determination of magnitude station corrections for a continental network of seismic stations

Summary A method for determining magnitude station corrections in a network of continental dimensions has been developed and tested for PV waves observed by eight selected Eurasian stations. Regional effects, observed for several stations, were taken into account. It appeared that station corrections could attain considerable values. The application of station corrections diminished both the dispersion of individual magnitude values and standard errors of mean network magnitudes.     

Frequency-direction analysis of geomagnetic pulsations

Summary Using the method of two-component spectral analysis of planar oscillation events by means of computer processing of A-t records, a series of about 100 samples of geomagnetic beating-type pulsations pc3 was treated. The quantitative data obtained on the internal structure of the pulsations (frequency spectra and polarization characteristics) were treated statistically. The pattern of the daily variations of the frequencies and amplitudes of the fundamental amplitude-dominating frequency components of the pulsations and the daily variations of the polarization characteristics of these components, the ellipticity of the polarization ellipses, the directions of the main axes of these ellipses and the sense of rotation of the disturbance vector along the ellipses were obtained.A part of the results was reported at the XVth General Assembly of the IUGG, Moscow, August 1971.     

On some modifications of Thomson-Haskell matrices for love waves

Summary In Haskell's formulation the dispersion equation is expressed by means of matrices, the elements of which are real or pure imaginary [2]. In the present paper different matrices have been found, which have only real elements.Dedicated to 90th Birthday of Professor Frantiek Fiala     

Frequency-direction analysis of geomagnetic pulsations

Summary A new method is presented of computer processing of amplitude-time records. The method is based on a two-component spectral analysis, suitable for investigating a planar stationary oscillatory event. The method is applied to the study of the fine structure of short-period geomagnetic pulsations. Apart from a semi-quantitative representation of the directional distribution of the pulsation event in the plane of oscillation, the proposed method enables one to obtain quantitative information on the frequency components, representing the pulsation — the distribution of the overall energy in the spectrum of the pulsation, the ellipticity of the polarization ellipses, the orientation of the major axes of the ellipses, and the sense of rotation of the disturbance vector.     

Effect of station conditions on amplitudes and periods of seismic waves

Summary Station corrections for Prhonice, relating to Praha, were determined for body and surface waves using observations of Kirnos seismographs. The time stability of the station corrections was investigated and the possible causes of observed instabilities were discussed. A systematic difference in periods recorded at the stations was found.Dedicated to Academician Alois Zátopek on His 65th Birthday     

The probability of occurrence of largest earthquakes in the European area

Summary TheGumbel's theory of largest values has been applied to the estimation of probability of occurrence and of return periods of largest earthquakes in the European area. For this study shallow shocks from the period 1901–1955 and from 15 earthquake zones were used. For each zone the largest magnitudes corresponding to one-year intervals were arranged in order of increasingM, grouped in classes and then the probabilitiesF(x _j) were calculated. The data plotted on the probability paper fit a straight line fairly well. The extrapolated lines yield the possibility of estimating large magnitudes which will be exceeded with a given probability, e.g. 1%. Such values were compared with largest magnitudes observed during the period 1901–1955. Their return periods indicate that in most regions the largest probable shock already occurred. Following the procedure ofEpstein-Lomnitz the coefficients and were calculated and compared with corresponding values ofa andb of the magnitude-frequency relation.