Grid travel-time tracing: Second-order method for the first arrivals in smooth media     

Luděk Klimeš 《Pure and Applied Geophysics》1996,148(3-4):539-563

A new computational scheme for calculating the first-arrival travel times on a rectangular grid of points is proposed. The new proposed method is of second-order accuracy. This means that the error of the calculated travel time is proportional to the second power of the grid spacing. The method should be sufficiently accurate for all applications in smooth seismic models. On the other hand, the method is not, in its present form, proposed for models with structural interfaces which make the method unstable and generate travel-time errors of the first order. Equations are also presented for the appropriate evaluation of the errors of calculated travel times to check their accuracy, and the proposed method is compared with other numerical methods. The method is developed, described and demonstrated in 2-D, but may also be extended to 3-D models and to general models with structural interfaces.  相似文献   

The inclusion of surface synoptic data in very short range predictions of convective events     

Zbyněk Sokol  Daniela Řezáčová  Petr Pešice 《Studia Geophysica et Geodaetica》1996,40(2):178-186

Summary Predictor vectors, including upper air as well as surface data, were used for categorical forecasting convective events over a subregion of the Czech territory, and the effect of including surface variables in the predictor vector was examined. While upper air data were considered as Perfect Prognosis, the surface data were successively included according to the time of their origin. The forecasting technique was based on linear multiple regression with learning, and the accuracy of the forecast was measured by the Critical Success Index. The input data from the three May-September periods in 1989–91 were used, and the first year served as the learning set. The aerological data from TEMP 12 UTC, simulating Perfect Prognosis, were the source of the upper air predictors. The performance of all, upper air, surface and combined, predictors were evaluated and compared. It turned out that the improvement of prediction accuracy due to the inclusion of surface variables was not negligible. Significant improvements were made in the forecasts of thunderstorm occurrence between 18 and 24 UTC.  相似文献   

Preface     

Ivan Pšenčík  Vlastislav Červený  Luděk Klimeš 《Pure and Applied Geophysics》1996,148(3-4):343-343

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Ellipsoidal Stokes Boundary-Value Problem with Ellipsoidal Corrections in the Boundary Condition     

Ardestani  Vahid E.  Martinec  Zdeněk 《Studia Geophysica et Geodaetica》2001,45(2):109-126

We would like to solve the Stokes boundary-value problem taking into consideration the ellipsoidal corrections in the boundary condition in ellipsoidal coordinates The original problem, i.e., the ellipsoidal Stokes boundary-value problem has been solved by Martinec and Grafarend (1997) We use the same philosophy expressed by Martinec (1998) to solve the spherical Stokes boundary-value problem with ellipsoidal corrections in the boundary condition We wish to show the magnitude of the integration kernel describing the effect of the ellipsoidal corrections in the boundary condition in a cap around the computational point.  相似文献   

Improvement of the accuracy of national coordinate systems using global systems     

Miloš Cimbálník 《Studia Geophysica et Geodaetica》1991,35(3):133-144

Summary Short history of the National Geodetic Reference System (NGRS), Common Network of the Socialist Countries (CNSC/42/58, Czech S-42), CNSC/42/83 (S-42/83) — result of the second adjustment of the CNSC in Moscow 1983; the state and accuracy of the existing horizontal control.Low accuracy of national coordinate systems, especially the scale. Conform transformation of the global system into the national and calculation of corrections (dx,dy) by quadratic, cubic or biquadratic transformation under condition of minimum differences between the national and new system. Adjustment of length and direction corrections, numerical example.The proposed method indicates the possibility of improving national coordinate systems on a permanent basis with the aid of improved and, therefore, changing global systems.  相似文献   

Long-term variations in geomagnetic and solar activities and secular variations of the geomagnetic field components     

Jaroslav Střeštík 《Studia Geophysica et Geodaetica》1991,35(1):1-6

Summary After the removal of the eleven-year periodicity, long-term patterns of the aa indices of geomagnetic activity and of Wolf's sunspot numbers are defined. The positions of maxima and minima exhibit the same regularities as the secular variations of the geomagnetic filed components. This result is associated with the motion of the Sun round the barycentre of the solar system.Presented at symposium Planet 88, Tihany, September 1988.  相似文献   

On the up-dating of the MSK-64 scale — A commentary     

V. Kárník 《Studia Geophysica et Geodaetica》1991,35(4):260-266

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Contribution to the experiment of axiomatizing the theory of turbulent diffusion     

Jiří Horák  Reviewer J. Navrátil 《Studia Geophysica et Geodaetica》1978,22(1):86-92

Summary The efforts to axiomatize the theory of turbulent diffusion, founded on the theory of Markovian random processes, are based on the principal logical algebraic aspects of the concept of modelling.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday  相似文献   

Thermal field in the Romanian Carpathian bend and some aspects of its interpretation     

Marius Visarion  Serban Veliciu  Mihai StefĂnescu  Reviewer V. Čermák 《Studia Geophysica et Geodaetica》1978,22(2):196-200

Summary Using heat flow and heat generation measurements together with deep seismic sounding and gravity data, a reasonable geothermal model has been constructed for the Romanian Carpathian Bend. At the level of the MOHO discontinuity the calculated temperatures exhibit conspicuous differences between inner and outer border of the Carpathian Bend and a horizontal gradient of 200–300 °C/100 km in the region is not to be excluded.Paper presented at the KAPG Symposium on Geothermics in Liblice, November 1976.  相似文献   

Contribution of the functional formulation of the problem of turbulence to the process of its algebraization     

Jiří Horák  Reviewer J. Navrátil 《Studia Geophysica et Geodaetica》1978,22(2):177-183

Summary The progressive development of the theory of turbulence is based on the formalism of characteristic functionals. Drawing on an incomplete analogy between the Hopf equation for these functionals and the equation for the quantized boson field, a system of fundamental principles of the theory of turbulence is proposed. This represents a set of statements which can be used in an attempt to classify the theory in the sense of its algebraization and, therefore, also its axiomatization.  相似文献