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  • Articles  (25)
  • earthquake swarms  (13)
  • climate change  (12)
  • Architecture, Civil Engineering, Surveying  (25)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 6 (1992), S. 69-80 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 272-291 
    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.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 327-335 
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 43 (1999), S. 87-106 
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 107-125 
    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.
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  • 6
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 40 (1996), S. 353-366 
    ISSN: 1573-1626
    Keywords: crustal structure ; Western Bohemia ; Vogtland ; earthquake swarms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary A layered model of the crustal and upper mantle structure for the region of the West-Bohemian earthquake swarms is proposed. This model represents a compilation of the results of deep seismic soundings, surface-wave investigations, and some local seismic measurements in the western regions of the Bohemian Massif.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 158-174 
    ISSN: 1573-1626
    Keywords: West Bohemia ; earthquake swarms ; location ; grid search ; homogeneous velocity models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract West Bohemian earthquake swarms are used to determine the parameters of simple homogeneous velocity models of the individual subregions of the given area, based on a group of earthquakes that occurred in these subregions. The grid search method is used for location. Models yielding the minimum sum of squares of the travel-time residua in locating the whole group of earthquakes in the given subregion are considered suitable. Relocation obtained by grid search is compared with that obtained by the FASTHYPO method. The computations indicate that the subregions under consideration can be, from the point of view of earthquake location, sufficiently represented by homogeneous models, but the models differ for the data from different subregions. The velocities of these models are given. The models under consideration are compared with some of the previously published 1-D models of the broader region of Western Bohemia.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 11 (1997), S. 17-34 
    ISSN: 1573-1650
    Keywords: rainfall regime ; Ganga basin ; weighted regression ; climate change ; trend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Data from three stations Agra, Dehradun and Dehli, were analyzed for evaluation of changes in rainfall and temperature regimes in the upper and middle parts of the Ganga basin in northern India. Long-term data on monsoon rainfall, the number of rainy days during the monsoon season, and the annual maximum temperature at these stations were included in the analysis. Nonparametric methods were employed to identify trends, if any, in these data. The analysis shows that the total monsoon rainfall and the number of rainy days during the monsoon season are on the decline, whereas the annual maximum temperature is on the rise. These changes are observed to have begun around the second half of the 1960's. The results point towards a possible change in the climatic regime of the Ganga basin that has far-reaching implications for the Indian economy.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Water resources management 11 (1997), S. 407-435 
    ISSN: 1573-1650
    Keywords: climate change ; hydrology ; water management ; water resources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Global climate change related to natural and anthropogenic processes has been the topic of concern and interest world wide. Despite ongoing research efforts, the climate predictions cannot be rated any better than speculative or possible scenarios whose probability of occurrence is, at the present stage, impossible to assess. One of the most significant impacts of the ‘greenhouse effect’ is anticipated to be on water resources, including different elements of the hydrologic cycle, water supply and demand, regional vulnerability, and water quality. Thus, the impact of climate change appears to be an additional component on top of the large number of existing water-related problems. The existence of the greenhouse effect, the increase of greenhouse gas emissions, and the rise of corresponding concentrations are things that are certain. However, their impacts on hydrology and water management are highly uncertain. In the latter area, one needs information on much smaller spatial and temporal scales than those used in climate studies. The objective of the present paper is to analyze the climate change impact on water resources in a system's perspective, to discuss scientific gaps, and challenge scientific issues. The role of different scales and uncertainties, as well as the hydrological view of global circulation models are also discussed. Our preparedness for probable global (climate) change is reviewed in terms of assessment, planning, design and adaptation.
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