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

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.     

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.     

On the discrete outer gravity field

Summary In the present paper the gravity field of the earth in the neighbourhood of the local disturbing masses is studied. The object of the method presented consists of the approximation of the disturbing potentialT _h , which fulfils Laplace's equation outside disturbing masses, on the earth's surface the fundamental boundary value condition of gravity and in infinity it is to be regular by the approximation of the disturbing potential (or by the discrete disturbing potential)T _h , which fulfils the respective finite difference approximation of Laplace's equation and the boundary value conditions in infinity and on the earth's surface. It is also shown that the approximation of the disturbing potentialT _h has the same properties as the disturbing potentialT. The method under consideration will be derived quite generally without any hypothesis about the distribution of the mass between the earth's surface and the geoid. It commences from the gravity data related to the earth's surface only-from the given geodetic measurements.     

A contribution to the numerical treatment of the electromagnetic field (H-polarization) in horizontally non-homogeneous models of the earth

Summary The problem of the electromagnetic field distribution, which is described by Helmholtz equation, is solved by treating the finite difference approximation. The field of H-polarization is studied on a bounded region consisting of blocks with different electrical conductivities separated by interfaces of a general form.     

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     

Seismically active fracture zones related to the western segment of the hellenic subduction

Summary A system of 12 seismically active fracture zones was delineated on the basis of the distribution of earthquake foci in the continental lithosphere in the western domain of the Hellenic area. The position and width of the outcrop, thickness, dip and maximum depth of the individual fracture zones were estimated and complemented by tectonic and geological evidence. The existence of the fracture zones was confirmed by the occurrence of historical disastrous earthquakes.     

Stress field in the earth's crust with curved boundaries

Summary A two-dimensional theory of gravitational stresses in the Earth's crust with curved boundaries is presented. The crust is modelled by an elastic plate lying on an elastic half-space. The solution obtained in the case of periodically varying boundaries is shown to be very sensitive to the ratio of both elastic parameters. Moreover, the geometrical configuration of both boundaries and their phase shift are of great importance for the resulting stress pattern.