Correlation between the Fluctuations in Worldwide Seismicity and in Atmospheric Carbon Pollution

The crucial stages in the geochemical evolution of the Earth’s crust, ocean, and atmosphere could be explained by the assumed low-energy nuclear reactions (LENR) that are triggered by seismic activity. LENR result in the fission of medium-weight elements accompanied by neutron emissions, involving Fe and Ni as starting elements, and C, N, O as resultants. Geochemical data and experimental evidences support the LENR hypothesis. The time series analysis highlighted significant correlation between the atmospheric CO2 growth rate and the global seismic-moment release rate, whereas the trending behavior was in response to the anthropogenic emissions. The fluctuations in the atmospheric CO2 growth rate time series were inexplicable in terms of anthropogenic emissions, but could be explained by the cycles of worldwide seismicity, which massively trigger LENR in the Earth’s crust. In this framework, LENR from active faults must be considered as a relevant cause of carbon formation and degassing of freshly-formed CO2 during seismic activity

Fractal scaling and crack-size effects on creep crack growth

Scaling effects on the creep crack growth behaviour are investigated by analyzing the results of compact tension (CT) tests on different-sized notched steel specimens appearing in the literature. Creep crack growth rate data are correlated to the elastic stress-intensity factor in terms of a Paris-type law, da/dt=C_0 K^q, where C_0 turns out to be a crack-size dependent coefficient of proportionality. Considering specimens with the same loading configuration (CT) and the same thickness, the observed crack-size effect on the creep crack growth rate is discussed on the basis of self-similarity considerations, and geometrically interpreted in terms of fractal tortuosity of the crack profile. A size-independent formulation of the creep crack growth law correlating renormalized quantities is finally deduced and confirmed by the experimental results

Criticality Hidden in Acoustic Emissions and in Changing Electrical Resistance during Fracture of Rocks and Cement-Based Materials

Acoustic emissions (AE) due to microcracking in solid materials permit the monitoring of fracture processes and the study of failure dynamics. As an alternative method of integrity assessment, measurements of electrical resistance can be used as well. In the literature, however, many studies connect the notion of criticality with AE originating from the fracture, but not with the changes in the electrical properties of materials. In order to further investigate the possible critical behavior of fracture processes in rocks and cement-based materials, we apply natural time (NT) analysis to the time series of AE and resistance measurements, recorded during fracture experiments on cement mortar (CM) and Luserna stone (LS) specimens. The NT analysis indicates that criticality in terms of electrical resistance changes systematically precedes AE criticality for all investigated specimens. The observed greater unpredictability of the CM fracture behavior with respect to LS could be ascribed to the different degree of material homogeneity, since LS (heterogeneous material) expectedly offers more abundant and more easily identifiable fracture precursors than CM (homogenous material). Non-uniqueness of the critical point by varying the detection threshold of cracking events is apparently due to finite size effects which introduce deviations from the self-similarity

AE monitoring and structural modelization of the Asinelli Tower in Bologna

The Acoustic Emission (AE) technique was used to assess the structural stability of the Asinelli Tower, the tallest building in the city of Bologna, which, together with the nearby tower, named Garisenda, is the renowned symbol of the city. AE is a passive, non-destructive structural evaluation technique based on the spontaneous emission of pressure waves by evolving fracture processes. The monitoring program was carried out with the aid of a USAM tool, which is part of the equipment used at the Fracture Mechanics Laboratory of the Department of Structural Engineering at the Politecnico di Torino. This tool makes it possible to conduct a complete analysis of AE signals, acquire a huge quantity of data from on site monitoring, and identify the microcracks triggering the damage processes in a structure. In the second part of the paper, the results from a preliminary linear analysis are presented, in order to assess the structural behavior of the tower. The cracking and crushing strengths of the masonry have both been compared with the calculated stresses. The numerical analysis gives a valuable picture of the modal response of the tower, providing useful hints for the prosecution of structural monitorin

Acoustic emission of the SyracuseAthena temple: timescale invariancefrom microcracking to earthquake

We show the results of acoustic-emission (AE) monitoring of the Cathedral of Syracuse in Sicily (Southern Italy), built around the surviving elements of a Doric temple dedicated to Athena from the 5th century BC. We wired up a single pillar of the 2500-year-old cathedral for four months and then compared the AE data with earthquake records, observing a time correlation between the AE bursts and the sequence of nearby earthquakes and a similar scaling for the related magnitude distributions. We found that the distribution of times between events —whether earthquakes or acoustic emissions— fell onto the same curve, over a wide range of timescales and energies, when scaled appropriately. A similar ‘universal scaling law’ has been shown for collections of earthquakes of a range of sizes in different regions, so the new results appear to extend the law to the much smaller energy scales of a single pillar. These pieces of evidence suggest a correlation between the aging process and the local seismic activity, and that more careful monitoring of the cathedral is warranted

Acoustic emission wireless monitoring of structures and infrastructure

The damage assessment of buildings is currently made visually. The few non-visual methodologies make use of wired devices, which are expensive, vulnerable, and time consuming to install. Systems based on wireless transmission should be cost efficient, easy to install, and adaptive to different types of structures and infrastructures. The Acoustic Emission (AE) technique is an innovative monitoring method useful to investigate the damage in large structures. It has the potential to detect damage, as well as to evaluate the evolution and the position of cracks. This paper shows the capability of a new data processing system based on a wireless AE equipment, very useful to long term monitoring of concrete and masonry structures. To this purpose, computer-based procedures, including an improved AE source location based on the Akaike algorithm, are implemented. These procedures are performed by automatic AE data processing and are used to evaluate the AE results in notched concrete beams subjected to three point bending loading conditions up to the final failure. In this case, the final output of the code returns a complete description of damage pattern and evolution of the monitored structure. In the most critical cases, or in some cases requiring long in situ observation periods, the AE monitoring method is fine tuned for a telematic procedure of processing AE data clouds to increase the safety of structures and infrastructural networks. Finally, the proposed AE monitoring system could be used to determine the seismic risk of civil constructions and monuments subjected to earthquakes

Acoustic emission wireless monitoring of structures and infrastructure

The damage assessment of buildings is currently made visually. The few non-visual methodologies make use of wired devices, which are expensive, vulnerable, and time consuming to install. Systems based on wireless transmission should be cost efficient, easy to install, and adaptive to different types of structures and infrastructures. The Acoustic Emission (AE) technique is an innovative monitoring method useful to investigate the damage in large structures. It has the potential to detect damage, as well as to evaluate the evolution and the position of cracks. This paper shows the capability of a new data processing system based on a wireless AE equipment, very useful to long term monitoring of concrete and masonry structures. To this purpose, computer-based procedures, including an improved AE source location based on the Akaike algorithm, are implemented. These procedures are performed by automatic AE data processing and are used to evaluate the AE results in notched concrete beams subjected to three point bending loading conditions up to the final failure. In this case, the final output of the code returns a complete description of damage pattern and evolution of the monitored structure. In the most critical cases, or in some cases requiring long in situ observation periods, the AE monitoring method is fine tuned for a telematic procedure of processing AE data clouds to increase the safety of structures and infrastructural networks. Finally, the proposed AE monitoring system could be used to determine the seismic risk of civil constructions and monuments subjected to earthquakes

Scaling in temporal occurrence of quasi-rigid-body vibration pulses due to macrofractures

We subjected the time series of quasi-rigid-body vibration pulses (elastic emissions) from laboratory fracture carried out by a piezoelectric accelerometer on concrete and rock specimens under uniaxial compression to statistical analysis. In both cases, we find that the waiting-time distribution can be described by a scaling law extending over several orders of magnitude. This law is indistinguishable from a universal scaling law recently proposed for the waiting-time distributions of acoustic emissions in heterogeneous materials and earthquakes, suggesting its general validity for fracture processes independent of modes and magnitude scales

Signal frequency distribution and natural-time analyses from acoustic emission monitoring of an arched structure in the Castle of Racconigi

The stability of an arch as a structural element in the thermal bath of King Charles Albert (Carlo Alberto) in the Royal Castle of Racconigi (on the UNESCO World Heritage List since 1997) was assessed by the acoustic emission (AE) monitoring technique with application of classical inversion methods to recorded AE data. First, damage source location by means of triangulation techniques and signal frequency analysis were carried out. Then, the recently introduced method of natural-time analysis was preliminarily applied to the AE time series in order to reveal a possible entrance point to a critical state of the monitored structural element. Finally, possible influence of the local seismic and microseismic activity on the stability of the monitored structure was investigated. The criterion for selecting relevant earthquakes was based on the estimation of the size of earthquake preparation zones. The presented results suggest the use of the AE technique as a tool for detecting both ongoing structural damage processes and microseismic activity during preparation stages of seismic events

Analysis of acoustic emission activity during progressive failure in heterogeneous materials : experimental and numerical investigation

This work focuses on an experimental and numerical investigation into monitoring damage in a cube-shaped concrete specimen under compression. Experimental monitoring uses acoustic emission (AE) signals acquired by two independent measurement apparatuses, and the same damage process is numerically simulated with the lattice discrete element method (LDEM). The results from the experiment and simulation are then compared in terms of their failure load, final configurations, and the evolution of global parameters based on AE signals, such as the b-value coefficient and the natural time approach. It is concluded that the results from the AE analysis present a significant sensitivity to the characteristics of the acquisition systems. However, natural time methods are more robust for determining such differences, indicating the same general tendency for all three data sets