Ludvík Urban - Academia.edu (original) (raw)

Papers by Ludvík Urban

Research paper thumbnail of Geomagnetic Field from T He e Arth's Core: Its Westward D Rift Rate and Some Probable Global-Tectonics I Mplications

Research paper thumbnail of Geomagnetic field: Contribution of higher harmonics to the variations of virtual pole positions

Studia Geophysica et Geodaetica, 1990

On the basis of the 1945 IGRF two sets of virtual geomagnetic poles have been computed and compar... more On the basis of the 1945 IGRF two sets of virtual geomagnetic poles have been computed and compared. The first set refers to a realistic model of the field; these virtual poles are all located in the north polar area. The second set refers to an artificial field containing higher harmonics only; these virtual poles are distributed over the Earth's surface as a whole. However both sets of virtual poles yield similar distributions of values of their space (and probably also time) variations.

Research paper thumbnail of Magnetic field measurements in India during the last two centuries

Studia Geophysica et Geodaetica, 1992

Summary The direction of the geomagnetic field has changed substantially less in India than in Eu... more Summary The direction of the geomagnetic field has changed substantially less in India than in Europe since the end of the 18th century.

Research paper thumbnail of Geomagnetic field from the Earth's core: Its westward drift rate and some probable global-tectonics implications

Studia Geophysica & Geodaetica, 1989

S u m m a r y: Sets o f virtual poles corresponding to sets o f geomagnetic field values at equid... more S u m m a r y: Sets o f virtual poles corresponding to sets o f geomagnetic field values at equidistant points, lying along circles o f latitude, were defined on the basis o f the 1980 1GRF extending to degree and order 8. Certain places on the Earth's surface yield virtual poles lying very close together. The segments o f the virtual pole paths, corresponding to these places, have a large curvature. The mentioned places o f the Earth's surface are supposed to be areas with a low rate o f the westward drift. They f o r m continuous zones that show a certain relation to global-tectonics features.

Research paper thumbnail of A method of estimating the westward drift velocity and possible correlation with features of global tectonics

Physics of the Earth and Planetary Interiors, 1990

... L. Urban and A. Janá ková. Department of Geophysics and Meteorology, Charles University, 180 ... more ... L. Urban and A. Janá ková. Department of Geophysics and Meteorology, Charles University, 180 00, Prague, Czechoslovakia. Received 4 May 1989; accepted 29 September 1989. Available online 14 October 2002. Abstract. ... B sin(q+t)] 344 I RHAN ANt) A JANAC (OVA TABLE I ...

Research paper thumbnail of Analytical Derivatives of Eigenfunctions, Energy Integral and Group Velocity for P-SV Waves

Research paper thumbnail of Haplogroup diversification of contemporary Croatian population

Introduction: Comprehensive Croatian Y-chromosome short tandem repeat (STR) haplotype database on... more Introduction: Comprehensive Croatian Y-chromosome short tandem repeat (STR) haplotype database on national and regional levels is important to get an insight into Y-chromosome genetic variability. The aim of this study was the detailed analysis of haplotype and haplogroup diversification in Croatian population. Methods: We carried out a statistical analysis of the data from previously performed genetic a analyses collected during routine forensic work by the Forensic Science Centre ‘‘Ivan Vucetic’’. A total of 1100 men from eastern, western, central, southern and northern Croatia were typed using AmpFISTR Yfiler PCR amplification kit. We estimated Y-chromosomal haplogroups from Croatian Y-STR haplotype data using Whit Atheys’ Haplogroup Predictor. Median-Joining Network (MJN) included all 17 Y-STR loci, and was constructed with Network 4.60 software. Software Splitstree 4.10 was used for creating the Neighbor-Joining (NJ) tree based on RST pair-wise distances between the Croatian an...

Research paper thumbnail of Verification of the Lithospheric Structure along Profile Uppsala-Prague Using Surface Wave Dispersion

Studia Geophysica Et Geodaetica, 1997

Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have b... more Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have been determined using records of several Italian earthquakes. To interpret the dispersion data, results of previous geophysical investigations in this region were first analyzed. Seven blocks of the crust and upper mantle were distinguished along the profile on the basis of deep seismic sounding and other seismic

Research paper thumbnail of P-SVmultimode summation differential seismograms for layered structures

Geophysical Journal International, 1998

We present a fast and accurate analytical method for computing di¡erential seismograms with respe... more We present a fast and accurate analytical method for computing di¡erential seismograms with respect to structural model parameters. The method adopts the P^SV-wave multimode summation formalism for laterally homogeneous layered media. The di¡erential seismograms calculated analytically do not su¡er from the numerical noise and instability a¡ecting numerical calculations. The frequency range for application of the method spans from regional-scale seismology to seismic engineering. Computationally, the proposed analytical method is equivalent to determining twomode spectra. In contrast to Nz1 (or 2N) mode spectra for a typical`brute-force' numerical ¢nite di¡erence approach, the method reduces the computations to 2/(Nz1) (if a one-sided perturbation ¢nite di¡erence scheme is used), which corresponds to a 90 per cent saving for 20 (N~20) layers. The speed and accuracy of the technique make it extremely attractive for structural parameter waveform inversions.

Research paper thumbnail of Effect of a simple mountain range on underground seismic motion

Geophysical Journal International, 1984

The influence of a simple mountain range on seismic ground motion is studied. A two-dimensional m... more The influence of a simple mountain range on seismic ground motion is studied. A two-dimensional model of the medium and vertically incident plane SH-waves are considered. Attention is devoted not only l o the wavefield along the Earth's surface, but also within the medium. The wavefield is computed in two steps: (I) the computation of the impulse response by the finite-difference method, (2) the computation of the response t o a time variation of the incident wave. approximately corresponding t o a 'hundred-yeai-' local earthquake a (the sitc. Numerical results (the impulse 1-esponse. the transfer function, the accelerograms, and their spectra) indicate strong spatial variability of the wavefield due to the topographical anomaly. The differences as large as 100 per cent in the peak amplitudes of the accelerograms, and of the order of 5 Hz in their predominant frequencies, at closely (-200 m) spaccd internal points of the medium have been found. Attention is focused also on the effect of causal absorption. Even unrealistically strong absorption seems to be unable t o reduce significantly the spatial variability of the ground niotion. caused by the topography. A variability like this. implying the occurrence of underground differential strains, might be of engineering inipoi-lance in the antiseismic desigti of underground structures (tunnels, for example) in mountainous seismic I-egions. The groundmotion variability along the surface of the mountain is considerably smaller than within the medium.

Research paper thumbnail of P-SVmultimode summation differential seismograms for layered structures

Geophysical Journal International, 1998

We present a fast and accurate analytical method for the calculation of differential seismograms ... more We present a fast and accurate analytical method for the calculation of differential seismograms resulting from perturbations in the structural model. The method adopts the P-SV wave multi-mode summation formalism for laterally homogeneous layered media. The differential seismograms calculated analytically do not suffer from the numerical noise and instability affecting the numerical calculations. The frequency range for the application of the method spans from regional scale seismology to seismic engineering. The computational overhead in the calculation of the partial derivatives amounts to the calculation of just one additional full mode-spectrum. The speed and accuracy of the technique makes it extremely attractive for structural parameters waveform inversions.

Research paper thumbnail of Predictions of magnetic fields for Uranus and Neptune

Studia Geophysica et Geodaetica, 1986

The magnetic moments of Uranus and Neptune haoe been predicted using different scaling laws of pl... more The magnetic moments of Uranus and Neptune haoe been predicted using different scaling laws of planetary magnetism. Tile predictions for Uranus cover a broad band of values from very weak magnetic fields (tidal relations) to moderate fields (thermal convection hypothesis). Therefore, the direct measurements of this field by Voyager 2 (January 1986) will be very important for testing the individual hapotheses.

Research paper thumbnail of Croatian national reference Y-STR haplotype database

Molecular Biology Reports, 2012

A reference Y-chromosome short tandem repeat (STR) haplotype database is needed for Y-STR match i... more A reference Y-chromosome short tandem repeat (STR) haplotype database is needed for Y-STR match interpretation as well as for national and regional characterization of populations. The aim of this study was to create a comprehensive Y-STR haplotype database of the Croatian contemporary population and to analyze substructure between the five Croatian regions. We carried out a statistical analysis of the data from previously performed genetic analyses collected during routine forensic work by the Forensic Science Centre "Ivan Vučetić". A total of 1,100 unrelated men from eastern, western, northern, southern and central Croatia were selected for the purpose of this study. Y-STRs were typed using the AmpFISTR Yfiler PCR amplification kit. Analysis of molecular variance calculated with the Y chromosome haplotype reference database online analysis tool included 16 population samples with 20,247 haplotypes. A total of 947 haplotypes were recorded, 848 of which were unique (89.5%). Haplotype diversity was 0.998, with the most frequent haplotype found in 9 of 1,100 men (0.82%). Locus diversity varied from 0.266 for DYS392 to 0.868 for DYS385. Discrimination capacity was 86.1%. Our results suggested high level of similarity among regional subpopulations within Croatia, except for mildly different southern Croatia. Relative resemblance was found with Bosnia and Herzegovina and Serbia. Whit Atheys' Haplogroup Predictor was used to estimate the frequencies of Y-chromosome haplogroups. I2a, R1a, E1b1b and R1b haplogroups were most frequent in all Croatian regions. These results are important in forensics and contribute to the population genetics and genetic background of the contemporary Croatian population.

Research paper thumbnail of Dynamical stability of convection cells in the upper mantle

Studia Geophysica et Geodaetica, 1988

Pe31oMe: ,ll~aygaeptaaa ~to~)eJtb menaoeo~ KoueeKuuu necotcu~aae~toFt ~cuOKoemu e nocmoam¢o~ ea3K... more Pe31oMe: ,ll~aygaeptaaa ~to~)eJtb menaoeo~ KoueeKuuu necotcu~aae~toFt ~cuOKoemu e nocmoam¢o~ ea3KocmblO ucnoab3yemca ~aa u3yueuua u3aceneuua me~euua 6o~tbutoeo •acutma6a. 06cyotcOa~omca pezyabmambt ~aa noneetcquu e eepxneft ~tanmuu 3e~tau. S u m m a r y : A two-dimensional flow model o f an incompressible fluid with constant viscosity has been used to study the changes in the large-scale flow pattern (aspect ratio 4). Implications f o r convection in the Earth's mantle are discussed.

Research paper thumbnail of Computation of analytical partial derivatives of phase and group velocities for Rayleigh waves with respect to structural parameters

Studia Geophysica Et Geodaetica - STUD GEOPHYS GEOD, 1993

Summary The analytical expressions used to compute the partial derivatives of phase and group vel... more Summary The analytical expressions used to compute the partial derivatives of phase and group velocity of Rayleigh waves with respect to the P- and S-wave velocity and the density are derived and the related computer code is developed. The results of the analytical computations were satisfactorily tested against numerically determined values. Several examples of partial derivatives for a given structural model are presented.

Research paper thumbnail of Geomagnetic Field from T He e Arth's Core: Its Westward D Rift Rate and Some Probable Global-Tectonics I Mplications

Research paper thumbnail of Geomagnetic field: Contribution of higher harmonics to the variations of virtual pole positions

Studia Geophysica et Geodaetica, 1990

On the basis of the 1945 IGRF two sets of virtual geomagnetic poles have been computed and compar... more On the basis of the 1945 IGRF two sets of virtual geomagnetic poles have been computed and compared. The first set refers to a realistic model of the field; these virtual poles are all located in the north polar area. The second set refers to an artificial field containing higher harmonics only; these virtual poles are distributed over the Earth's surface as a whole. However both sets of virtual poles yield similar distributions of values of their space (and probably also time) variations.

Research paper thumbnail of Magnetic field measurements in India during the last two centuries

Studia Geophysica et Geodaetica, 1992

Summary The direction of the geomagnetic field has changed substantially less in India than in Eu... more Summary The direction of the geomagnetic field has changed substantially less in India than in Europe since the end of the 18th century.

Research paper thumbnail of Geomagnetic field from the Earth's core: Its westward drift rate and some probable global-tectonics implications

Studia Geophysica & Geodaetica, 1989

S u m m a r y: Sets o f virtual poles corresponding to sets o f geomagnetic field values at equid... more S u m m a r y: Sets o f virtual poles corresponding to sets o f geomagnetic field values at equidistant points, lying along circles o f latitude, were defined on the basis o f the 1980 1GRF extending to degree and order 8. Certain places on the Earth's surface yield virtual poles lying very close together. The segments o f the virtual pole paths, corresponding to these places, have a large curvature. The mentioned places o f the Earth's surface are supposed to be areas with a low rate o f the westward drift. They f o r m continuous zones that show a certain relation to global-tectonics features.

Research paper thumbnail of A method of estimating the westward drift velocity and possible correlation with features of global tectonics

Physics of the Earth and Planetary Interiors, 1990

... L. Urban and A. Janá ková. Department of Geophysics and Meteorology, Charles University, 180 ... more ... L. Urban and A. Janá ková. Department of Geophysics and Meteorology, Charles University, 180 00, Prague, Czechoslovakia. Received 4 May 1989; accepted 29 September 1989. Available online 14 October 2002. Abstract. ... B sin(q+t)] 344 I RHAN ANt) A JANAC (OVA TABLE I ...

Research paper thumbnail of Analytical Derivatives of Eigenfunctions, Energy Integral and Group Velocity for P-SV Waves

Research paper thumbnail of Haplogroup diversification of contemporary Croatian population

Introduction: Comprehensive Croatian Y-chromosome short tandem repeat (STR) haplotype database on... more Introduction: Comprehensive Croatian Y-chromosome short tandem repeat (STR) haplotype database on national and regional levels is important to get an insight into Y-chromosome genetic variability. The aim of this study was the detailed analysis of haplotype and haplogroup diversification in Croatian population. Methods: We carried out a statistical analysis of the data from previously performed genetic a analyses collected during routine forensic work by the Forensic Science Centre ‘‘Ivan Vucetic’’. A total of 1100 men from eastern, western, central, southern and northern Croatia were typed using AmpFISTR Yfiler PCR amplification kit. We estimated Y-chromosomal haplogroups from Croatian Y-STR haplotype data using Whit Atheys’ Haplogroup Predictor. Median-Joining Network (MJN) included all 17 Y-STR loci, and was constructed with Network 4.60 software. Software Splitstree 4.10 was used for creating the Neighbor-Joining (NJ) tree based on RST pair-wise distances between the Croatian an...

Research paper thumbnail of Verification of the Lithospheric Structure along Profile Uppsala-Prague Using Surface Wave Dispersion

Studia Geophysica Et Geodaetica, 1997

Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have b... more Experimental dispersion curves of Rayleigh and Love waves along the Uppsala-Prague profile have been determined using records of several Italian earthquakes. To interpret the dispersion data, results of previous geophysical investigations in this region were first analyzed. Seven blocks of the crust and upper mantle were distinguished along the profile on the basis of deep seismic sounding and other seismic

Research paper thumbnail of P-SVmultimode summation differential seismograms for layered structures

Geophysical Journal International, 1998

We present a fast and accurate analytical method for computing di¡erential seismograms with respe... more We present a fast and accurate analytical method for computing di¡erential seismograms with respect to structural model parameters. The method adopts the P^SV-wave multimode summation formalism for laterally homogeneous layered media. The di¡erential seismograms calculated analytically do not su¡er from the numerical noise and instability a¡ecting numerical calculations. The frequency range for application of the method spans from regional-scale seismology to seismic engineering. Computationally, the proposed analytical method is equivalent to determining twomode spectra. In contrast to Nz1 (or 2N) mode spectra for a typical`brute-force' numerical ¢nite di¡erence approach, the method reduces the computations to 2/(Nz1) (if a one-sided perturbation ¢nite di¡erence scheme is used), which corresponds to a 90 per cent saving for 20 (N~20) layers. The speed and accuracy of the technique make it extremely attractive for structural parameter waveform inversions.

Research paper thumbnail of Effect of a simple mountain range on underground seismic motion

Geophysical Journal International, 1984

The influence of a simple mountain range on seismic ground motion is studied. A two-dimensional m... more The influence of a simple mountain range on seismic ground motion is studied. A two-dimensional model of the medium and vertically incident plane SH-waves are considered. Attention is devoted not only l o the wavefield along the Earth's surface, but also within the medium. The wavefield is computed in two steps: (I) the computation of the impulse response by the finite-difference method, (2) the computation of the response t o a time variation of the incident wave. approximately corresponding t o a 'hundred-yeai-' local earthquake a (the sitc. Numerical results (the impulse 1-esponse. the transfer function, the accelerograms, and their spectra) indicate strong spatial variability of the wavefield due to the topographical anomaly. The differences as large as 100 per cent in the peak amplitudes of the accelerograms, and of the order of 5 Hz in their predominant frequencies, at closely (-200 m) spaccd internal points of the medium have been found. Attention is focused also on the effect of causal absorption. Even unrealistically strong absorption seems to be unable t o reduce significantly the spatial variability of the ground niotion. caused by the topography. A variability like this. implying the occurrence of underground differential strains, might be of engineering inipoi-lance in the antiseismic desigti of underground structures (tunnels, for example) in mountainous seismic I-egions. The groundmotion variability along the surface of the mountain is considerably smaller than within the medium.

Research paper thumbnail of P-SVmultimode summation differential seismograms for layered structures

Geophysical Journal International, 1998

We present a fast and accurate analytical method for the calculation of differential seismograms ... more We present a fast and accurate analytical method for the calculation of differential seismograms resulting from perturbations in the structural model. The method adopts the P-SV wave multi-mode summation formalism for laterally homogeneous layered media. The differential seismograms calculated analytically do not suffer from the numerical noise and instability affecting the numerical calculations. The frequency range for the application of the method spans from regional scale seismology to seismic engineering. The computational overhead in the calculation of the partial derivatives amounts to the calculation of just one additional full mode-spectrum. The speed and accuracy of the technique makes it extremely attractive for structural parameters waveform inversions.

Research paper thumbnail of Predictions of magnetic fields for Uranus and Neptune

Studia Geophysica et Geodaetica, 1986

The magnetic moments of Uranus and Neptune haoe been predicted using different scaling laws of pl... more The magnetic moments of Uranus and Neptune haoe been predicted using different scaling laws of planetary magnetism. Tile predictions for Uranus cover a broad band of values from very weak magnetic fields (tidal relations) to moderate fields (thermal convection hypothesis). Therefore, the direct measurements of this field by Voyager 2 (January 1986) will be very important for testing the individual hapotheses.

Research paper thumbnail of Croatian national reference Y-STR haplotype database

Molecular Biology Reports, 2012

A reference Y-chromosome short tandem repeat (STR) haplotype database is needed for Y-STR match i... more A reference Y-chromosome short tandem repeat (STR) haplotype database is needed for Y-STR match interpretation as well as for national and regional characterization of populations. The aim of this study was to create a comprehensive Y-STR haplotype database of the Croatian contemporary population and to analyze substructure between the five Croatian regions. We carried out a statistical analysis of the data from previously performed genetic analyses collected during routine forensic work by the Forensic Science Centre "Ivan Vučetić". A total of 1,100 unrelated men from eastern, western, northern, southern and central Croatia were selected for the purpose of this study. Y-STRs were typed using the AmpFISTR Yfiler PCR amplification kit. Analysis of molecular variance calculated with the Y chromosome haplotype reference database online analysis tool included 16 population samples with 20,247 haplotypes. A total of 947 haplotypes were recorded, 848 of which were unique (89.5%). Haplotype diversity was 0.998, with the most frequent haplotype found in 9 of 1,100 men (0.82%). Locus diversity varied from 0.266 for DYS392 to 0.868 for DYS385. Discrimination capacity was 86.1%. Our results suggested high level of similarity among regional subpopulations within Croatia, except for mildly different southern Croatia. Relative resemblance was found with Bosnia and Herzegovina and Serbia. Whit Atheys' Haplogroup Predictor was used to estimate the frequencies of Y-chromosome haplogroups. I2a, R1a, E1b1b and R1b haplogroups were most frequent in all Croatian regions. These results are important in forensics and contribute to the population genetics and genetic background of the contemporary Croatian population.

Research paper thumbnail of Dynamical stability of convection cells in the upper mantle

Studia Geophysica et Geodaetica, 1988

Pe31oMe: ,ll~aygaeptaaa ~to~)eJtb menaoeo~ KoueeKuuu necotcu~aae~toFt ~cuOKoemu e nocmoam¢o~ ea3K... more Pe31oMe: ,ll~aygaeptaaa ~to~)eJtb menaoeo~ KoueeKuuu necotcu~aae~toFt ~cuOKoemu e nocmoam¢o~ ea3KocmblO ucnoab3yemca ~aa u3yueuua u3aceneuua me~euua 6o~tbutoeo •acutma6a. 06cyotcOa~omca pezyabmambt ~aa noneetcquu e eepxneft ~tanmuu 3e~tau. S u m m a r y : A two-dimensional flow model o f an incompressible fluid with constant viscosity has been used to study the changes in the large-scale flow pattern (aspect ratio 4). Implications f o r convection in the Earth's mantle are discussed.

Research paper thumbnail of Computation of analytical partial derivatives of phase and group velocities for Rayleigh waves with respect to structural parameters

Studia Geophysica Et Geodaetica - STUD GEOPHYS GEOD, 1993

Summary The analytical expressions used to compute the partial derivatives of phase and group vel... more Summary The analytical expressions used to compute the partial derivatives of phase and group velocity of Rayleigh waves with respect to the P- and S-wave velocity and the density are derived and the related computer code is developed. The results of the analytical computations were satisfactorily tested against numerically determined values. Several examples of partial derivatives for a given structural model are presented.