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  • 1
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    Imaging slow failure in triaxially deformed Etna basalt using 3D acoustic-emission location and X-ray computed tomography (2007)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: We have deformed basalt from Mount Etna (Italy) in triaxial compression tests under an effective confining pressure representative of conditions under a volcanic edifice (40 MPa), and at a constant strain rate of 5 10 6 s 1. Despite containing a high level of pre-existing microcrack damage, Etna basalt retains a high strength of 475 MPa. We have monitored the complete deformation cycle through contemporaneous measurements of axial strain, pore volume change, compressional wave velocity change and acoustic emission (AE) output. We have been able to follow the complete evolution of the throughgoing shear fault without recourse to any artificial means of slowing the deformation. Locations of AE events over time yields an estimate of the fault propagation velocity of between 2 and 4 mm/s-1. We also find excellent agreement between AE locations and post-test images from X-ray microtomography scanning that delineates deformation zone architecture. Citation: Benson, P. M., B. D. Thompson, P. G. Meredith, S. Vinciguerra, and R. P. Young (2007), Imaging slow failure in triaxially deformed Etna basalt using 3D acoustic-emission location and X-ray computed tomography
    Description: Published
    Description: L03303
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: fault imaging ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of mining-induced microseismic events at Strathcona Mine, Subdury, Canada (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 455-474 
    Details
    ISSN: 1420-9136
    Keywords: Mining-induced events ; seismic monitoring ; focal mechanism ; source parameters ; Strathcona hard rock mine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Rockbursts and mining-induced seismic events have serious socio-economic consequences for the Canadian mining industry, as their mines are extended to greater depths. Automatic multichannel monitoring systems (Electro-Lab MP250s) are routinely, used to detect the arrival times of seismic waves radiated by mining-induced events and sensed on an array of single component transducers installed throughout a mine. These arrival times are then used to locate the events and produce maps of areas of high activity for use in mine planning and design. This approach has limitations in that, it does not allow a detailed analysis of source mechanisms, which could be extracted if whole waveform signals are recorded and analyzed. A major research project, sponsored by the Natural Sciences and Engineering Research Council of Canada (NSERC) with the collaboration of the Canadian mining industry, is aimed at enhancing existing mine seismic monitoring technology in Canada, in order to carry out more advanced processing of data to obtain fundamental scientific information on mining-induced seismic events This paper describes preliminary results from seismic monitoring experiments carried out in a hard rock nickel mine in Sudbury, Canada. Existing seismic monitoring instrumentation was enhanced with a low cost microcomputer-based whole waveform seismic acquisition system. Some of the signals recorded during this experiment indicate anisotropic wave propagation through the mine rock masses, as observed by the splitting of shear waves and the relative arrival of two shear waves polarized in directions which may be related to the structural fabric and/or state of stress in the rock mass. Analysis of compressional wave first motion shows the predominance of shear events, as indicated by focal mechanism studies and is confirmed by spectral analysis of the waveforms. The source parameters were estimated fro typical low magnitude localized microseismic events during the initial monitoring experiments. The seismic moment of these events varied between 106 N.m and 2.108 N.m. with a circular source radius of between 1 m and 2 m with an estimated stress drop of the order of 1 MPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874519
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  • 3
    Electronic Resource
    Electronic Resource
    Sequential velocity imaging and microseismic monitoring of mining-induced stress change (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 421-447 
    Details
    ISSN: 1420-9136
    Keywords: Sequential velocity imaging ; temporal velocity changes ; mining-induced seismicity ; velocity-seismicity association
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Sequential imaging of the temporal changes inP-wave velocity offers a practical tool to monitor a rock mass. Using established correlations between the location of seismic events and velocity structure, the temporal seismic potential characteristics of the rock may be monitored. Furthermore, the temporal velocity differences isolate the time dependent factors effecting velocity such as stress, while cancelling static factors such as lithology. Various sequential imaging techniques were compared with respect to accuracy. Differences between successive velocity images were found to have relatively high associated error estimates. However, images of velocity differences calculated from measured travel time delays between successive velocity surveys were found to have lower error estimates. In particular, travel time delays measured using cross-correlation techniques resulted in the most accurate sequential image. Two 3D sequential imaging studies were carried out at Strathcona Mine in Sudbury, Ontario, Canada. Results of the average static images indicated an association between the location of induced microseismicity and a zone of both high velocity and high gradient. Additional examples are described from the global seismology literature which also show a similar correlation between seismicity and velocity structure. We attribute this association to an interrelated stress and strength effect. The Strathcona Mine sequential images show zones of significantly decreased velocity in regions of concentrated microseismic activity, which are postulated to be indications of localized destressing and relaxation of the clamping forces resulting in the microseismicity. The zones of decreased velocity corresponded to an increase in the velocity gradient. One of the case studies also shows an increase in velocity in a zone of high static velocity, which is later the site of am N 2.5 mining-induced seismic tremor. The increase in velocity is believed to correspond to a region of stress concentration, resulting in the subsequent seismic tremor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879945
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  • 4
    Electronic Resource
    Electronic Resource
    Geotomographic imaging in the study of mining induced seismicity (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 571-596 
    Details
    ISSN: 1420-9136
    Keywords: Mining-induced seismicity ; passive monitoring method ; geotomographic imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Geotomographic imaging is a technique which allows seismic waves to be used to gain information about the internal structure of rock masses, in a way conceptually similar to medical CAT scanning. Traditional approaches to the study of mining-induced seismic phenomena have concentrated on using passive monitoring methods. This paper gives an overview of the developments in the acquisition, processing and interpretation of geotomographic data and outlines how images can be used in conjunction with passive techniques to study mining-induced seismicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874526
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of source region properties on scaling relations forM〈0 events (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 721-739 
    Details
    ISSN: 1420-9136
    Keywords: Non-similar scaling relations ; fracture complexity ; depth dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Excavation induced seismic events with moment magnitudesM〈0 are examined in an attempt to determine the role geology, excavation geometry, and stress have on scaling relations. Correlations are established based on accurate measurements of excavation geometry and methodology, stress regime, rock mass structure, local tectonics, and seismic locations. Scaling relations incorporated seismic moments and source radii obtained by spectral analysis, accounting for source, propagation, and site effects, and using Madariaga's dynamic circular fault model. Observations suggest that the interaction of stresses with pre-existing fractures, fracture complexity and depth of events are the main factors influencing source characteristics and scaling behaviour. Self-similar relationships were found for events at similar depths or for weakly structured rock masses with reduced clamping stresses, whereas a non-similar behaviour was found for events with increasing depth or for heavily fractured zones under stress confinement. Additionally, the scaling behaviour for combined data sets tended to mask the non-similar trends. Overall, depth and fracture complexity, initially thought as second order effects, appear to significantly influence source characteristics of seismic events withM〈0 and consequently favour a non-similar earthquake generation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879960
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  • 6
    Electronic Resource
    Electronic Resource
    Mining-induced microseismicity: Monitoring and applications of imaging and source mechanism techniques (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 697-719 
    Details
    ISSN: 1420-9136
    Keywords: Induced seismicity ; tomography ; b values ; source parameters ; moment tensor inversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The study of microseismicity in mines provides an ideal method for remote volumetric sampling of rock masses. The nature and uniqueness of microseismic monitoring is outlined in the context of acquisition hardware and software requirements. Several topics are used to highlight the potential for novel applications of microseismicity and to outline areas where further study is required. These topics reflect some of the current interest areas in seismology, namelyb values and source parameters, fault-plane solutions, modes of failure and moment tensor inversion, imaging and seismicityvelocity correlations. These studies suggest potential correlations between zones of high seismic velocity, high microseismic activity and maximal stress drops, which can be interpreted spatially to be the locations of highly stressed ground with a potential for rock bursting. Fault-plane solutions are shown to be useful in determining the slip potential of various joint sets in a rock mass. Source parameter studies and moment tensor analysis clearly show the importance of non-shear components of failure, andb values for microseismicity appear to be magnitude-limited and related to spatial rather than temporal variations in effective stress levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879959
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  • 7
    Electronic Resource
    Electronic Resource
    Laboratory and field investigations of rockburst phenomena using concurrent geotomographic imaging and acoustic emission/microseismic techniques (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 647-659 
    Details
    ISSN: 1420-9136
    Keywords: Rockburst phenomena ; geotomographic imaging ; microseismic monitoring systems ; waveform acquisition system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The progress made on three phases of a research project, started in 1986 to investigate mining induced seismicity/rockburst phenomena using concurrent geotomographic imaging and microseismic monitoring techniques, is described. Phase I is the geotomographic software development and laboratory calibration trials. Phase II is the enhancement of traditional microseismic monitoring instrumentation with a waveform acquisition system, so that source mechanism studies can be carried out on mining induced seismic events. Phase III is the field trials of the hybrid technique which will be used to monitor changing rock mass physical properties, in response to mining. Preliminary results from all three phases are given, together with an outline of current and future research planned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874530
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  • 8
    Electronic Resource
    Electronic Resource
    Space-time correlations ofb values with stress release (1992)
    Springer
    Pure and applied geophysics 139 (1992), S. 449-462 
    Details
    ISSN: 1420-9136
    Keywords: Low magnitude seismicity ; b values ; stress release estimates ; forescast stress patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A total of 1503 events for a 2-month period associated with am N 2.6 rockburst is investigated for possible space-time correlations between low magnitude (−1.1 to −0.4)b values and several estimates of stress (static stress drop, apparent stress, and dynamic stress). Spatial variations of decreasingb values were found to be well correlated with increasing stress release estimates for time intervals prior to the rockburst and following the aftershock sequence. The strongest correlation tob value was with the dynamic stress drop, having correlation coefficients of 0.87 and 0.79 for the two intervals, respectively. The rockburst was found to actually occur at the intersection of the spatial coordinates corresponding to the largest gradient inb value. Based on these correlations, we conclude that the low magnitude seismicity is an indicator of the stress state within the rock mass, and can be used to study and forecast stress patterns in the vicinity of an impending major event. Time variations, however, did not show the same clear correlations and these are discussed in terms of departure from steady state conditions. Regardless, our results favour the use ofb values in a spatial, context rather than in a time analysis approach, and we consider thatb values provide valuable information regarding the changing stress conditions within the seismogenic volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879946
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  • 9
    Electronic Resource
    Electronic Resource
    Asthma, Atopy, and Genetic Linkage (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 629 (1991), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1991.tb37957.x
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  • 10
    Electronic Resource
    Electronic Resource
    The electrical conductivity of aqueous tetraalkylammonium halide solutions under hydrostatic pressure (1968)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 72 (1968), S. 1763-1767 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100851a065
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