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  • Articles  (37)
  • earthquake swarms  (13)
  • climate change  (12)
  • dispersion  (12)
  • Architecture, Civil Engineering, Surveying  (37)
  • 1
    Electronic Resource
    Electronic Resource
    Micro-scale modelling in the study of plume evolution in heterogeneous media (1987)
    Springer
    Stochastic environmental research and risk assessment 1 (1987), S. 263-279 
    Details
    ISSN: 1436-3259
    Keywords: Porous media ; heterogeneity ; groundwater ; dispersion ; stochastic theory ; plume evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The migration of contaminants in heterogeneous aquifers involves dispersive processes that act at different scales. The interaction of these processes as a plume evolves can be studied by micro-scale modelling whereby two scales, a local- or micro-scale and an aquifer- or macro-scale, are covered simultaneously. Local-scale dispersive processes are represented through the local dispersion coefficient in the transport equation, while large-scale dispersion due to heterogeneities is represented through the resolution of the flow field and the diffusive exchange between streamtubes. The micro-scale model provides both the high degree of resolution compatible with local-scale processes, and the extent required for the approach to asymptotic conditions, using grids of up to a million nodal points. The model is based on the dual potential-streamfunction formulation for flow, and the transport problem is formulated in a natural coordinate system provided by the flownet. Simulations can be used to verify stochastic theories of dispersion, without the restrictive assumptions inherent in the theory. For the two-dimensional case, results indicate convergence of the effective dispersivity to the theoretical macrodispersivity value. Convergence takes place within a travel distance of about 50 correlation lengths of the hydraulic conductivity field. However, the approach taken to asymptotic conditions, as well as the macrodispersivity value, may differ for different realizations of the same medium. The influence of early-time events such as plume splitting on the asymptotic convergence remains to be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543098
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  • 2
    Electronic Resource
    Electronic Resource
    Statistical validation of GCM-simulated climates for the U.S. Great Lakes and the C.I.S. Emba and Ural River basins (1992)
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 69-80 
    Details
    ISSN: 1436-3259
    Keywords: Hydrology ; global circulation models ; statistics ; climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Many researchers use outputs from large-scale global circulation models of the atmosphere to assess hydrological and other impacts associated with climate change. However, these models cannot capture all climate variations since the physical processes are imperfectly understood and are poorly represented at smaller regional scales. This paper statistically compares model outputs from the global circulation model of the Geophysical Fluid Dynamics Laboratory to historical data for the United States' Laurentian Great Lakes and for the Emba and Ural River basins in the Commonwealth of Independent States (C.I.S.). We use maximum entropy spectral analysis to compare model and data time series, allowing us to both assess statistical predictabilities and to describe the time series in both time and frequency domains. This comparison initiates assessments of the model's representation of the real world and suggests areas of model improvement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581676
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  • 3
    Electronic Resource
    Electronic Resource
    A resumé of nonlocal transport theories (1995)
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 105-116 
    Details
    ISSN: 1436-3259
    Keywords: Nonlocal ; transport ; dispersion ; heterogeneity ; integro-differential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Analysis from a number of different perspectives has shown diffusion and dispersion in natural porous formations to generally be nonlocal in character, i.e., the mass balance involves integro-partial differential equations. Only in certain asymptotic limits do these laws localize to classical partial differential equations. Compiled within is a resume of nonlocal laws that our group has developed over the last few years for systems with physical, chemical and biological heterogeneity. Analytical tools used to obtain these laws are nonequilibrium and equilibrium statistical mechanics, and first-order spectral-perturbation methods. This paper is an expansion of the material presented at the Waterloo conference held in the memory of Dr. Unny.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01585601
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  • 4
    Electronic Resource
    Electronic Resource
    Dispersion of toxic combustion products from large fires (1992)
    Springer
    Fire technology 28 (1992), S. 168-173 
    Details
    ISSN: 1572-8099
    Keywords: Fires ; combustion products ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Conclusions The computer models discussed here are used by MHAU to give an initial indication of the possible hazards to the local population from the dispersion of combustion products from large fires. Agreement between the computer model and the wind tunnel data is encouraging, particularly at relatively low values of the buoyancy flux parameterF U −3 L −1. HSE is proposing to commence large-scale dispersion trials in the open air in the near future. It is hoped that this will enable greater confidence to be had in the predictions of the computer models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01857943
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  • 5
    Electronic Resource
    Electronic Resource
    Verification of the Litho-spheric Structure along Profile Uppsala-Prague Using Surface Wave Dispersion (1997)
    Springer
    Studia geophysica et geodaetica 41 (1997), S. 15-28 
    Details
    ISSN: 1573-1626
    Keywords: lithospheric structure ; dispersion ; surface waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract 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 data. Layered models were proposed for these blocks. Computation of Rayleigh and Love waves shows a large differentiation of theoretical dispersion curves for the northern (Precambrian) and southern (Palaeozoic) part of the profile. A laterally inhomogeneous model for theUppsala - Prague profile, composed of the seven blocks, satisfies the surface wave data for the profile. Moreover, a mean layered model for the whole profile has also been proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023332522678
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis of State of Stress During The 1997 Earthquake Swarm In Western Bohemia (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 272-291 
    Details
    ISSN: 1573-1626
    Keywords: West Bohemia ; earthquake swarms ; stress analysis ; Gephart and Forsyth method ; fault plane discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract Focal mechanisms of 70 events of the January 1997 earthquake swarm were analysed using the Gephart and Forsyth method to determine the state of stress in the West Bohemia/Vogtland region and to reveal possible stress variations during the swarm activity. The method was applied to the whole set of 70 focal mechanisms and to several subsets distinguishing magnitudes of events and the spatial and temporal distribution of the swarm. The three representative stress models A (σ 1 ,A: 0/45 (az/dip), σ 2 A: 134/35, σ 3 A: 243/25), B (σ 1 ,B: 162/38, σ 2 B: 263/14, σ 3 B: 10/49), and C (σ 1 C: 135/30, σ 2 C: 1/50, σ 3 C: 239/23) which could characterise the state of stress in the region were found. Model C can be considered to be the most probable stress model because of its consistency with the European stress field. The results of the stress analysis applied to the individual subsets of focal mechanisms indicate that the state of stress was more uniform during the first phase of the swarm. To distinguish between the fault plane and the auxiliary plane of fault plane solutions a statistical approach was used. The results showed that the fault planes striking NW-SE and dipping 45° to NE were activated during the swarm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022171027896
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  • 7
    Electronic Resource
    Electronic Resource
    Subsurface Temperature Changes Due to the Crustal Magmatic Activity – Numerical Simulation (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 327-335 
    Details
    ISSN: 1573-1626
    Keywords: magma intrusions ; crustal temperatures ; earthquake swarms ; Bohemian Massif
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract Geothermal aspects of the hypothesis, relating the earthquake swarms in the West Bohemia/Vogtland seismoactive region to magmatic activity, are addressed. A simple 1-D geothermal model of the crust was used to assess the upper limit of the subsurface heating caused by magma intrusion at the assumed focal depth of 9 km. We simulated the process by solving the transient heat conduction equation numerically, considering the heat of magma crystallization to be gradually released in the temperature interval 1100°C to 900°C. The temperature field prior to the intrusion was in steady-state with a surface temperature of 10°C and heat flow of 80 mWm −2 , the temperature at the 9 km depth was 270°C. The results suggest that the temperature and heat flow in the uppermost 1 km of the crust begin to grow 100 ka after the intrusion emplacement only, and that the amplitudes of the changes for the realistic lateral extent (a few kilometres) of the intrusion are very small. It was also found that the rate of magma solidification depends strongly on the thickness of the intrusion. It takes about 100 years for a 50 m thick sill to cool down from 1100°C to 600°C, which value represents the lower limit of the solidus temperature. The same cooling takes only 60 days if the sill is 2 m thick. If the nature of the strongly reflected boundaries, interpreted from the January 1997 Nový Kostel seismograms, is connected with the fresh emplacement of magma, the calculated cooling rates have a predictive potential for the temporal changes of the waveforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022127312875
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  • 8
    Electronic Resource
    Electronic Resource
    Magma Intrusions and Earthquake Swarm Occurrence in the Western Part of the Bohemian Massif (1999)
    Springer
    Studia geophysica et geodaetica 43 (1999), S. 87-106 
    Details
    ISSN: 1573-1626
    Keywords: earthquake swarms ; magma intrusions ; fluids ; Bohemian Massif ; induced seismicity ; WEBNET ; KTB ; 9HR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract We are proposing a hypothesis that earthquake swarms in the West Bohemia/Vogtland seismoactive region are generated by magmatic activity currently transported to the upper crustal layers. We assume that the injection of magma and/or related fluids and gases causes hydraulic fracturing which is manifested as an earthquake swarm at the surface. Our statements are supported by three spheres of evidence coming from the western part of the Bohemian Massif: characteristic manifestations of recent geodynamic activity, the information from the neighbouring KTB deep drilling project and from the 9HR seismic reflection profile, and the detailed analysis of local seismological data. (1) Recent manifestations of geodynamic activity include Quaternary volcanism, rich CO 2 emissions, anomalies of mantle-derived 3 He, mineral springs, moffets, etc. (2) The fluid injection experiment in the neighbouring KTB deep borehole at a depth of 9 km induced hundreds of micro-earthquakes. This indicates that the Earth's crust is near frictional failure in the western part of the Bohemian Massif and an addition of a small amount of energy to the tectonic stress is enough to induce an earthquake. Some pronounced reflections in the closely passing 9HR seismic reflection profile are interpreted as being caused by recent magmatic sills in the crust. (3) The local broadband seismological network WEBNET provides high quality data that enable precise localization of seismic events. The events of the January 1997 earthquake swarm are confined to an extremely narrow volume at depths of about 9 km. Their seismograms display pronounced reflections of P- and S-waves in the upper crust. The analysis of the process of faulting has disclosed a considerable variability of the source mechanism during the swarm. We conclude that the mechanism of intraplate earthquake swarms generated by magma intrusions is similar to that of induced seismicity. As the recent tectonic processes and manifestations of geodynamic activity are similar in European areas with repeated earthquake swarm occurrence (Bohemian Massif, French Massif Central, Rhine Graben), we assume that magma intrusions and related fluid and gas release at depths of about 10 km are the universal cause of intraplate earthquake swarm generation
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023366210017
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  • 9
    Electronic Resource
    Electronic Resource
    The Western Bohemia/Vogtland Region in the Light of the Webnet Network (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 107-125 
    Details
    ISSN: 1573-1626
    Keywords: West Bohemia ; earthquake swarms ; local seismic network ; local magnitude ; local earthquake waveform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract The local network of digital seismic stations WEBNET monitors the seismic activitv of practically the whole region of Western Bohemia/Vogtland swarms. The network consists of ten short-period stations and one very broadband station. The paper describes the configuration of the network, instrumental equipment and the basic parameters of the stations. The method of and formula for computing the local magnitudes from the WEBNET and KRASLICE seismograms are also given. Based on continuous WEBNET observations in the period 1995-1999, we were able to improve the model of temporal and spatial energy release in the region, the principal characteristics of which are summarised in the paper. Apart from direct P and S waves, the WEBNET seismograms also contain other significant P- and S-type waves, provisionally interpreted as reflected PxP, SxS and SxP waves. The fundamental characteristics of these waves are given in the paper, and tentative mechanisms of their origination are discussed. The large residua in the travel times of the P and S waves, and the discrepancies in the seismograms recorded at stations located east of the principal focal zone are pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022198406514
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  • 10
    Electronic Resource
    Electronic Resource
    Refined Locations of The Swarm Earthquakes In The Nový Kostel Focal Zone and Spatial Distribution of The January 1997 Swarm In Western Bohemia, Czech Republic (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 210-226 
    Details
    ISSN: 1573-1626
    Keywords: earthquake swarms ; cluster of foci ; relative location ; cluster analysis ; multiplet events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract In order to improve the accuracy of the spatial distribution of earthquake foci in the principal Novy Kostel focal zone, refined focal locations of about 1500 micro-earthquakes of the 1991 – 1997 period were determined using the relative Master-Event location method. To estimate the reduction in the scatter of located hypocentres, the results were compared with those obtained by routinely used FASTHYPO method and cluster analysis (the nearest-neighbour method) was applied to the located foci to evaluate the spatial distribution of the foci. Based on the results of refined location and of the cluster analysis, a concept of seismic energy release in space and time in the main focal zone was developed. Especially the January 1997 earthquake swarm was studied in detail: 946 events were located with the Master-Event location method, and the dimensions and geometry of focal clusters were determined. Type analysis was applied to waveforms to divide approximately 800 located events into eight multiplet groups to each of which a characteristic source mechanism was assigned. The spatial distribution of the foci as well as of the eight types of source mechanisms was revealed in this way and also the planes fitting the clusters of foci with two predominant source mechanisms were determined fairly well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022162826079
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