scholarly journals Experimental evidence of the compatibility of the cumulative electromagnetic energy release data, with the hierarchical models for the catastrophic fracturing process

2011 ◽  
Vol 11 (6) ◽  
pp. 1605-1608 ◽  
Author(s):  
D. Mastrogiannis ◽  
V. Hadjicontis ◽  
C. Mavromatou
Keyword(s):  
Energy Release ◽  
Prediction Method ◽  
Electromagnetic Emission ◽  
Cumulative Energy ◽  
Emission Data ◽  
Electromagnetic Pulses ◽  
Fracturing Process ◽  
Release Data ◽  
Electromagnetic Signals ◽  
The Moment

Abstract. In this paper, we performed experiments of uniaxial compression of granite samples and recorded time series of electromagnetic pulses during the evolution of the catastrophic fracturing process. The cumulative energy release of the electromagnetic emission (EME) up to the critical point at the moment of rupture was then calculated. It was shown, that the validity of the proposed hierarchy models for the catastrophic fracturing process of composite materials, in analogy to critical phenomena, can be experimentally established not only via acoustic emission data, but via electromagnetic emission data as well. The above conclusion could be a useful tool for the improvement of the earthquake prediction method, based on precursory electromagnetic signals.

scholarly journals Relaxation creep model of impending earthquake

2001 ◽  
Vol 44 (2) ◽  
Author(s):  
V. A. Morgounov
Keyword(s):  
Strain Rate ◽  
Signal To Noise Ratio ◽  
Electromagnetic Emission ◽  
Creep Model ◽  
Current Status ◽  
Alternative View ◽  
Rate Dependent ◽  
Tectonic Earthquakes ◽  
Prediction Reliability ◽  
The Moment

The alternative view of the current status and perspective of seismic prediction studies is discussed. In the problem of ascertainment of the uncertainty relation Cognoscibility-Unpredictability of Earthquakes, priorities of works on short-term earthquake prediction are defined due to the advantage that the final stage of nucleation of earthquake is characterized by a substantial activation of the process while its strain rate increases by the orders of magnitude and considerably increased signal-to-noise ratio. Based on the creep phenomenon under stress relaxation conditions, a model is proposed to explain different images of precursors of impending tectonic earthquakes. The onset of tertiary creep appears to correspond to the onset of instability and inevitably fails unless it is unloaded. At this stage, the process acquires the self-regulating character and to the greatest extent the property of irreversibility, one of the important components of prediction reliability. Data in situ suggest a principal possibility to diagnose the process of preparation by ground measurements of strain-rate-dependent parameters, like electromagnetic emission, etc. Laboratory tests of the measurements of acoustic and electromagnetic emission in the rocks under constant strain in the condition of self-relaxed stress until the moment of fracture are discussed in context. It was obtained that electromagnetic emission precedes but does not accompany the phase of macrocrack development.

Prediction of Deformation to Thin Ship Panels for Different Heat Sources

2001 ◽  
Vol 17 (02) ◽  
pp. 52-61
Author(s):  
H.C. Kuo ◽  
L.J. Wu
Keyword(s):  
Plate Thickness ◽  
Prediction Method ◽  
Steel Plates ◽  
Data Series ◽  
Heat Sources ◽  
Skilled Workers ◽  
Forming Process ◽  
Shipbuilding Industry ◽  
On Line ◽  
The Moment

The increasing use of thin steel plates in manufacturing and the shipbuilding industry has given rise to several issues: massive deformation problems, the need for many skilled workers, and the expense of costs for straightening in on-line processes. This study explains the results of experiments and predicts techniques for the control of deformation in thin panels. The objective of this paper is to explain the use of the G(1,1) Grey method to predict deformation. Bending and buckling are usually the dominant modes of deformation in heat working. It follows angular deformation. De- formation due to different heat sources is discussed. In this paper, laser and torch are used in different constraints, for example, free-free beam and cantilever beam. Many important factors include tiny adjustments during the heat forming process, such as changing the moment speed, intensity of input heating, plate thickness and heating path, to improve manufacture techniques and to predict deformation by data series. For the prediction of deformation, a method to estimate input heating of laser and torch is introduced. The proposed prediction method can be used during the forming process simply and efficiently.

scholarly journals Full-waveform based complete moment tensor inversion and source parameter estimation from downhole microseismic data for hydrofracture monitoring

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. WC103-WC116 ◽  
Author(s):  
Fuxian Song ◽  
M. Nafi Toksöz
Keyword(s):  
Hydraulic Fracturing ◽  
Moment Tensor ◽  
Fracture Plane ◽  
Far Field ◽  
Field Range ◽  
Full Waveform ◽  
Microseismic Data ◽  
Fracturing Process ◽  
The Moment ◽  
Additional Constraints

Downhole microseismic monitoring is a valuable tool in understanding the efficacy of hydraulic fracturing. Inverting for the moment tensor has gained increasing popularity in recent years as a way to understand the fracturing process. Previous studies utilize only part of the information in the waveforms, such as direct P- and S-wave amplitudes, and make far-field assumptions to determine the source mechanisms. The method is hindered in downhole monitoring, when only limited azimuthal coverage is available. In this study, we develop an approach to invert for complete moment tensor using full-waveform data recorded at a vertical borehole. We use the discrete wavenumber integration method to calculate full wavefields in the layered medium. By using synthetic data, we find that, at the near-field range, a stable, complete moment tensor can be retrieved by matching the waveforms without additional constraints. At the far-field range, we discover that the off-plane moment tensor component is poorly constrained by waveforms recorded at one well. Therefore, additional constraints must be introduced to retrieve the complete moment tensor. We study the inversion with three different types of constraints. For each constraint, we investigate the influence of velocity model errors, event mislocations, and data noise on the extracted source parameters by a Monte Carlo study. We test our method using a single well microseismic data set obtained during the hydraulic fracturing of the Bonner sands in East Texas. By imposing constraints on the fracture strike and dip range, we are able to retrieve the complete moment tensor for events in the far-field. Field results suggest that most events have a dominant double-couple component. The results also indicate the existence of a volumetric component in the moment tensor. The derived fracture plane orientation generally agrees with that derived from the multiple event location.

scholarly journals The results of experimental studies of VLF–ULF electromagnetic emission by rock samples due to mechanical action

2013 ◽  
Vol 1 (6) ◽  
pp. 7821-7842
Author(s):  
A. A. Panfilov
Keyword(s):  
Laboratory Experiments ◽  
Experimental Studies ◽  
Electromagnetic Emission ◽  
Mechanical Action ◽  
Frequency Range ◽  
Impact Action ◽  
Rock Samples ◽  
Electric Component ◽  
Electromagnetic Signals ◽  
The Impact

Abstract. The paper presents the results of laboratory experiments on electromagnetic emission excitation (electric component of electromagnetic field) by rock samples due to different forms of mechanical stress applications. It was shown that samples generate electric impulses with different spectra when the impact action, gradual loading or dynamic friction is applied. It was ascertained that level and spectral compositions of signals, generated by rock samples, change with increasing quantity of hits. It was found that strong electromagnetic signals, generated while rock samples were fracturing, were accompanied by repetitive weak, but perceptible variations of the electric field intensity in short frequency range.

scholarly journals MODELLING THE ENERGY RELEASE PROCESS OF AFTERSHOCKS

2017 ◽  
Vol 50 (3) ◽  
pp. 1341
Author(s):  
D. Gospodinov
Keyword(s):  
Stochastic Model ◽  
Energy Release ◽  
Aftershock Sequence ◽  
Suggested Model ◽  
Cumulative Energy ◽  
Release Process ◽  
Aftershock Sequences ◽  
Strain Release ◽  
Loma Prieta ◽  
Benioff Strain

A stochastic model for the study of Benioff strain release during aftershock sequences is suggested. The stochastic model is elaborated after a compound Poisson process and is applied on data of the M7.1 Ocober 18, 1989 Loma Prieta aftershock sequence in northern California, USA. The temporal evolution of the number of events is first modelled by the Restricted Epidemic Type Aftershock Sequence (RETAS) model and then the identified best fit model is incorporated in the energy release analysis. The suggested model is based on the assumptions that there is no relation between the magnitude and the occurrence time of an event first and second, that there is no relation between the magnitude of a certain event and magnitudes of previous events. The obtained results from the examination of the energy release reveal that the suggested model makes a good fit of the aftershock Benioff strain release and enables a more detailed study by identifying possible deviations between data and model. The real cumulative energy release values surpass the expected model ones, which proves that aftershocks, stronger than forecasted by the model, are clustered at the beginning of the Loma Prieta sequence.

scholarly journals Comparative analysis of acoustic and electromagnetic emissions of rocks

2021 ◽  
Vol 929 (1) ◽  
pp. 012013
Author(s):  
V N Klyuchkin ◽  
V A Novikov ◽  
V I Okunev ◽  
V A Zeigarnik
Keyword(s):  
Comparative Analysis ◽  
Uniaxial Compression ◽  
High Stress ◽  
Electromagnetic Emission ◽  
Rock Failure ◽  
Dynamic Rupture ◽  
Block Model ◽  
Rock Samples ◽  
Electromagnetic Emissions ◽  
Electromagnetic Signals

Abstract Comparative analysis of acoustic and electromagnetic emissions recorded during the intact rock samples deformation and dynamic rupture of simulated crustal fault is presented. Specialized machines for uniaxial compression and shear tests of rock samples with identical data acquisition systems for both test cases were employed. Increase of acoustic emission was observed accompanied by significant rise of intensity and amplitude of electromagnetic signals at high stress of the rock samples under the uniaxial compression or dynamic failure in the spring-block model. Such correlation is consistent with the previous conclusions that an increase of electromagnetic emission may be considered as a rock failure precursor. Any specific characteristics of the detected electromagnetic signals to be used for prediction of impending rock failure or the earthquake fault rupture were not found. The similarity of electromagnetic signals and their spectra obtained at the press equipment and the spring-block model suggests that in both cases, the signals observed are generated by the crack formations and shear. The electromagnetic emission appeared only in dry samples. The samples saturated by water with the salinity of over 0.1% demonstrated no electromagnetic emission.

scholarly journals Stress induced polarization currents and electromagnetic emission from rocks and ionic crystals, accompanying their deformation

2004 ◽  
Vol 4 (5/6) ◽  
pp. 633-639 ◽  
Author(s):  
V. Hadjicontis ◽  
C. Mavromatou ◽  
D. Ninos
Keyword(s):  
Piezoelectric Materials ◽  
Electromagnetic Emission ◽  
Induced Polarization ◽  
Ionic Crystals ◽  
Uniaxial Deformation ◽  
Plausible Model ◽  
Plausible Answer ◽  
Preparatory Stage ◽  
Electromagnetic Signals ◽  
Electric Signals

Abstract. A crucial question of the scientific community nowadays, concerns the existence of electric signals preceding earthquakes. In order to give a plausible answer to this question, we carried out two kinds of laboratory experiments of uniaxial deformation of ionic crystals and rock samples: a) In the first kind, stress induced polarization currents are detected and recorded. Our experimental results showed not only the existence of stress induced polarization currents before the fracture of the samples, but the possibility of the propagation of these signals, as well, through conductive channels, for distances much longer than the source dimensions. b) In the second, acoustic and electromagnetic signals are detected and recorded in the frequency range from 1KHz to some MHz. The mechanism of generation of these signals is shown to be different for those emitted from piezoelectric and from non-piezoelectric materials. A plausible model is also suggested, on the compatibility of our laboratory results with the processes occurring in the earth during the earthquake preparatory stage.

Acoustic emission measurements and lattice simulations of microfracture events in spruce

Holzforschung ◽  
2010 ◽  
Vol 64 (4) ◽  
Author(s):  
Edwin Nagy ◽  
Eric N. Landis ◽  
William G. Davids
Keyword(s):  
Acoustic Emission ◽  
Fracture Energy ◽  
Energy Release ◽  
Lattice Model ◽  
Failure Modes ◽  
Mechanical Damage ◽  
Peak Strain ◽  
Cumulative Energy ◽  
Ae Energy ◽  
Total Fracture

Abstract A statistical lattice model was developed to investigate the energy associated with damage and failure of wood. The model incorporates several important morphological aspects of wood such as grain direction, early wood percentage and grain geometry. The model was developed to investigate progressive damage under enforced boundary displacements and has been adapted to predict fracture energy related phenomena. In this particular study, notched specimens were loaded in uniaxial tension while monitored by a passive acoustic emission (AE) measurement system. The energy associated with the mechanical damage was measured by the AE instruments and compared with the energy released by ruptured elements in the lattice model. Cumulative energy release was tracked as a function of specimen load and deformation in both model and experiment. A ratio was established between the cumulative AE energy released at the first drop in load and the cumulative fracture energy released when the model load-deformation relationship becomes significantly non-linear. An additional ratio was established between the total fracture energy measured prior to 50% of peak strain and the total fracture energy measured prior to peak strain. The magnitudes of these energy release ratios vary owing to a change in failure modes between the short model and the larger specimens; however, the shape of the AE energy release curve up to failure coincides well with that predicted by the model simulations.

Quantifying the effect of fuel reduction treatments on fire behavior in boreal forests

2013 ◽  
Vol 43 (1) ◽  
pp. 97-102 ◽  
Author(s):  
B.W. Butler ◽  
R.D. Ottmar ◽  
T.S. Rupp ◽  
R. Jandt ◽  
E. Miller ◽  
...  
Keyword(s):  
Energy Release ◽  
Boreal Forests ◽  
Fire Hazard ◽  
Control Treatment ◽  
Maximum Temperature ◽  
Fire Intensity ◽  
Prescribed Burn ◽  
Fuel Treatments ◽  
Cumulative Energy ◽  
Maximum Heat

Mechanical (e.g., shearblading) and manual (e.g., thinning) fuel treatments have become the preferred strategy of many fire managers and agencies for reducing fire hazard in boreal forests. This study attempts to characterize the effectiveness of four fuel treatments through direct measurement of fire intensity and forest floor consumption during a single prescribed burn. The treatments included (1) thinning trees and removing debris (THIN-REMOVE-1 and -2), (2) thinning trees and burning the debris onsite, (3) shearblading and leaving the debris in place (SHEAR), and (4) shearblading and piling the debris in windrows (SHEAR-ROW). Fire burned through treatments 1, 3, and 4 and one control unit. The highest fire intensities (maximum temperature of 1150 °C, maximum heat flux of 227 kW·m–2, and fire cumulative energy release of 4277 J·m–2) were measured in the control. Treatment 1 exhibited a peak temperature of 267 °C, peak heating of 16 kW·m–2, and cumulative energy release of 2600 J·m–2. Treatments 3 and 4 exhibited peak temperatures of 170 and 66 °C, peak heating of 51 and 3 kW·m–2, and cumulative energy release of 2500 and 1800 J·m–2, respectively. The thinned treatment showed the most significant impact in the context of reduced heat release.

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