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The main goal of an Earthquake Early Warning System (EEWS) is to alert before the arrival of damaging waves using the first seismic arrival as a proxy, thus becoming an important operational tool for real-time seismic risk management on a short timescale. EEWSs are based on the use of scaling relations between parameters measured on the initial portion of the seismic signal after the arrival of the first wave. To explore the plausibility of EEWSs around the Eastern Gulf of Corinth and Western Attica, amplitude and frequency-based parameters, such as peak displacement (Pd), the integral of squared velocity (
Filippos Vallianatos; Andreas Karakonstantis; Nikolaos Sakelariou. Estimation of Earthquake Early Warning Parameters for Eastern Gulf of Corinth and Western Attica Region (Greece). First Results. Sensors 2021, 21, 5084 .
AMA StyleFilippos Vallianatos, Andreas Karakonstantis, Nikolaos Sakelariou. Estimation of Earthquake Early Warning Parameters for Eastern Gulf of Corinth and Western Attica Region (Greece). First Results. Sensors. 2021; 21 (15):5084.
Chicago/Turabian StyleFilippos Vallianatos; Andreas Karakonstantis; Nikolaos Sakelariou. 2021. "Estimation of Earthquake Early Warning Parameters for Eastern Gulf of Corinth and Western Attica Region (Greece). First Results." Sensors 21, no. 15: 5084.
The Western Gulf of Corinth (WGoC) exhibits significant seismicity patterns, combining intense microseismic background activity with both seismic swarms and short-lived aftershock sequences. Herein, we present a catalogue of ~9000 events, derived by manual analysis and double-difference relocation, for the seismicity of the WGoC during 2013–2014. The high spatial resolution of the hypocentral distribution permitted the delineation of the activated structures and their relation to major mapped faults on the surface. The spatiotemporal analysis of seismicity revealed a 32-km-long earthquake migration pattern, related to pore-pressure diffusion, triggering moderate mainshock-aftershock sequences, as fluids propagated eastwards in the course of ~15 months. The anisotropic properties of the upper crust were examined through automatic shear-wave splitting (SWS) analysis, with over 2000 SWS measurements at local stations. An average fast shear-wave polarization direction of N98.8° E ± 2.8° was determined, consistent with the direction of the maximum horizontal regional stress. Temporal variations of normalized time-delays between fast and slow shear-waves imply alterations in the level of stress or microcrack fluid saturation during the long-lasting pore-pressure diffusion episode, particularly before major events. The present study provides novel insights regarding seismicity patterns, active fault structures, anisotropic properties of the upper crust and triggering mechanisms of seismicity in the WGoC.
Vasilis Kapetanidis; Georgios Michas; George Kaviris; Filippos Vallianatos. Spatiotemporal Properties of Seismicity and Variations of Shear-Wave Splitting Parameters in the Western Gulf of Corinth (Greece). Applied Sciences 2021, 11, 6573 .
AMA StyleVasilis Kapetanidis, Georgios Michas, George Kaviris, Filippos Vallianatos. Spatiotemporal Properties of Seismicity and Variations of Shear-Wave Splitting Parameters in the Western Gulf of Corinth (Greece). Applied Sciences. 2021; 11 (14):6573.
Chicago/Turabian StyleVasilis Kapetanidis; Georgios Michas; George Kaviris; Filippos Vallianatos. 2021. "Spatiotemporal Properties of Seismicity and Variations of Shear-Wave Splitting Parameters in the Western Gulf of Corinth (Greece)." Applied Sciences 11, no. 14: 6573.
In the present work, a multiscale post-seismic relaxation mechanism, based on the existence of a distribution in relaxation time, is presented. Assuming an Arrhenius dependence of the relaxation time with uniform distributed activation energy in a mesoscopic scale, a generic logarithmic-type relaxation in a macroscopic scale results. The model was applied in the case of the strong 2015 Lefkas Mw6.5 (W. Greece) earthquake, where continuous GNSS (cGNSS) time series were recorded in a station located in the near vicinity of the epicentral area. The application of the present approach to the Lefkas event fits the observed displacements implied by a distribution of relaxation times in the range τmin ≈ 3.5 days to τmax ≈ 350 days.
Filippos Vallianatos; Vassilis Sakkas. Multiscale Post-Seismic Deformation Based on cGNSS Time Series Following the 2015 Lefkas (W. Greece) Mw6.5 Earthquake. Applied Sciences 2021, 11, 4817 .
AMA StyleFilippos Vallianatos, Vassilis Sakkas. Multiscale Post-Seismic Deformation Based on cGNSS Time Series Following the 2015 Lefkas (W. Greece) Mw6.5 Earthquake. Applied Sciences. 2021; 11 (11):4817.
Chicago/Turabian StyleFilippos Vallianatos; Vassilis Sakkas. 2021. "Multiscale Post-Seismic Deformation Based on cGNSS Time Series Following the 2015 Lefkas (W. Greece) Mw6.5 Earthquake." Applied Sciences 11, no. 11: 4817.
The statistical patterns occurring on the threshold of an earthquake, in the transition stage immediately before and after the rupture, still remain unclear. Investigating the dynamical features of surface deformation a few days before and after the earthquake co-seismic rupture are crucial to understand the mechanics of the earthquake process. In the present work, we study surface displacements as estimated using continuous GNSS measurements in the vicinity of the 2020 Mw7.0 Samos (Greece) strong, shallow earthquake. The GNSS time series before and after the Mw7.0 earthquake in SAMO (belonging to METRICA SA HexagonSmartNet commercial network) station demonstrate significant surface deformation in the broader epicentral area. We further analyze the surface displacement increments a few days before and after the Samos Mw7.0 earthquake using the non-extensive statistical physics (NESP) framework, which could provide a frame to study the complexity of the earthquake process. The results of the analysis suggest that the statistical distribution of ground displacement increments presents asymptotic power-law behavior that deviates from the standard Gaussian function. Instead, the observed distributions can be described by the q-Gaussian function derived in the NESP framework, for q-values in the range of 1.10–1.15. In addition, the statistical pattern that was obtained from the analysis is further discussed in terms of superstatistics, indicating that the ground displacement increments a few days before and after the Mw7.0 earthquake correspond to a system with high enough degrees of freedom of the order of 13–15. Furthermore, for comparison, a four years record of continuous GNSS measurements was analyzed using NESP. The results support the non-extensive character of displacement increments using a four years period of recordings suggesting long-range temporal correlations.
Filippos Vallianatos; Georgios Michas; Vassilis Sakkas; Eleni I. Partheniou. First evidence of the non-extensive character of pre- and post-seismic deformation of Samos (2020) Mw7.0 earthquake. Acta Geophysica 2021, 1 -11.
AMA StyleFilippos Vallianatos, Georgios Michas, Vassilis Sakkas, Eleni I. Partheniou. First evidence of the non-extensive character of pre- and post-seismic deformation of Samos (2020) Mw7.0 earthquake. Acta Geophysica. 2021; ():1-11.
Chicago/Turabian StyleFilippos Vallianatos; Georgios Michas; Vassilis Sakkas; Eleni I. Partheniou. 2021. "First evidence of the non-extensive character of pre- and post-seismic deformation of Samos (2020) Mw7.0 earthquake." Acta Geophysica , no. : 1-11.
On October 30, 2020, a strong and shallow earthquake (Mw = 7.0) hit Samos, an island on the eastern edge of the Aegean Sea (Greece). The epicenter was located on the north offshore of the Greek island of Samos. The goal of our work is to provide a first analysis of the scaling properties observed in the aftershock sequence as reported until December 31, 2020, as numerous seismic clusters activated. Our analysis is focused on the main of the clusters observed in the East area of the activated fault zone and strongly related with the mainshock’s fault. The aftershock sequence follows the Omori law with a value of p ≈ 1.01 for the main cluster which is remarkably close to a logarithmic evolution. The analysis of interevent times distribution, based on non-extensive statistical physics indicates a system in an anomalous equilibrium with a crossover from anomalous (q > 1) to normal (q = 1) statistical mechanics, as great interevent times approached. A discussion of the crossover observed, is given in terms of superstatistics. In addition, the obtained value q ≈ 1.67 suggests a system with one degree of freedom. Furthermore, a scaling of the migration of aftershock zone as a function of the logarithm of time is discussed in terms of rate strengthening rheology that govern the evolution of afterslip process.
Filippos Vallianatos; Kyriaki Pavlou. Scaling properties of the Mw7.0 Samos (Greece), 2020 aftershock sequence. Acta Geophysica 2021, 1 -18.
AMA StyleFilippos Vallianatos, Kyriaki Pavlou. Scaling properties of the Mw7.0 Samos (Greece), 2020 aftershock sequence. Acta Geophysica. 2021; ():1-18.
Chicago/Turabian StyleFilippos Vallianatos; Kyriaki Pavlou. 2021. "Scaling properties of the Mw7.0 Samos (Greece), 2020 aftershock sequence." Acta Geophysica , no. : 1-18.
Strong motion sensor networks deployed in metropolitan areas are able to provide valuable information for civil protection Decision Support Systems (DSSs) aiming to mitigate seismic risk and earthquake social-economic impact. To this direction, such a network is installed and real-time operated in Chania (Crete Island, Greece), city located in the vicinity of the seismically active south front of the Hellenic Subduction Zone. A blend of both traditional and advanced analysis techniques and interpretation methods of strong ground motion data are presented, studying indicative cases of Chania shaking due to earthquakes in the last couple years. The orientation independent spectral acceleration as well as the spatial distribution of the strong ground motion parameters such as the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Peak Ground Displacement (PGD) and Arias Ιntensity observed at the urban area of Chania are presented with the use of a Geographic Information System (GIS) environment. The results point to the importance of the strong ground motion networks as they can provide valuable information on earthquake hazards prior to and after detrimental seismic events to feed rapid systems supporting civil protection decisions for prevention and emergency response.
Georgios Chatzopoulos; Ilias Papadopoulos; Filippos Vallianatos; John Makris; Maria Kouli. Strong Ground Motion Sensor Network for Civil Protection Rapid Decision Support Systems. Sensors 2021, 21, 2833 .
AMA StyleGeorgios Chatzopoulos, Ilias Papadopoulos, Filippos Vallianatos, John Makris, Maria Kouli. Strong Ground Motion Sensor Network for Civil Protection Rapid Decision Support Systems. Sensors. 2021; 21 (8):2833.
Chicago/Turabian StyleGeorgios Chatzopoulos; Ilias Papadopoulos; Filippos Vallianatos; John Makris; Maria Kouli. 2021. "Strong Ground Motion Sensor Network for Civil Protection Rapid Decision Support Systems." Sensors 21, no. 8: 2833.
In the present work we apply the cBΩ thermodynamic model to study the diffusion of Si in stishovite crystal at high pressure and in a wide temperature range. According to this model, the point defect activation Gibbs free energy is expressed as a function of the bulk properties of the material, i.e., gact = cBΩ, where B is the isothermal bulk modulus, Ω is the mean atomic volume, and c is a dimensionless constant. In this way, other important point defect parameters, such as the activation volume vact, the activation entropy sact, and the activation enthalpy hact may be estimated if the thermoelastic properties of the material are known over a wide temperature and pressure range. Our calculations are based on previously reported self-diffusion coefficients in stishovite single crystals measured at 14 GPa and at temperatures from 1400 to 1800 °C, in the [110] and [001] directions, by Shatskiy et al. (Am. Mineral. 2010, 95, 135–43). Furthermore, the EOS of stishovite, proposed by Wang et al. (J. Geophys. Res. 2012, 117, B06209) has been used for the accurate implementation of the cBΩ model. Our results suggest that the aforementioned point defect parameters exhibit considerable temperature dependence over the studied temperature range (1000–2000 °C). The estimated activation volumes (4.4–5.3 cm3/mol, in the range of 1400–1800 °C) are in agreement with reported experimental results. Our study confirms the potential of the cBΩ model for the theoretical investigation of diffusion processes in minerals, in order to overcome the experimental difficulties and the lack of experimental diffusion data in mantle conditions.
Vassilios Saltas; Filippos Vallianatos. Silicon Self-Diffusion in Stishovite: Calculations of Point Defect Parameters Based on the cBΩ Thermodynamic Model. Environmental Sciences Proceedings 2021, 6, 6 .
AMA StyleVassilios Saltas, Filippos Vallianatos. Silicon Self-Diffusion in Stishovite: Calculations of Point Defect Parameters Based on the cBΩ Thermodynamic Model. Environmental Sciences Proceedings. 2021; 6 (1):6.
Chicago/Turabian StyleVassilios Saltas; Filippos Vallianatos. 2021. "Silicon Self-Diffusion in Stishovite: Calculations of Point Defect Parameters Based on the cBΩ Thermodynamic Model." Environmental Sciences Proceedings 6, no. 1: 6.
Fracturing processes within solid Earth materials are inherently a complex phenomenon so that the underlying physics that control fracture initiation and evolution still remain elusive. However, universal scaling relations seem to apply to the collective properties of fracturing phenomena. In this article we present a statistical physics approach to fracturing based on the framework of non-extensive statistical physics (NESP). Fracturing phenomena typically present intermittency, multifractality, long-range correlations and extreme fluctuations, properties that motivate the NESP approach. Initially we provide a brief review of the NESP approach to fracturing and earthquakes and then we analyze stress and stress direction time series within Arctic sea ice. We show that such time series present large fluctuations and probability distributions with “fat” tails, which can exactly be described with the q-Gaussian distribution derived in the framework of NESP. Overall, NESP provide a consistent theoretical framework, based on the principle of entropy, for deriving the collective properties of fracturing phenomena and earthquakes.
Filippos Vallianatos; Georgios Michas. Complexity of Fracturing in Terms of Non-Extensive Statistical Physics: From Earthquake Faults to Arctic Sea Ice Fracturing. Entropy 2020, 22, 1194 .
AMA StyleFilippos Vallianatos, Georgios Michas. Complexity of Fracturing in Terms of Non-Extensive Statistical Physics: From Earthquake Faults to Arctic Sea Ice Fracturing. Entropy. 2020; 22 (11):1194.
Chicago/Turabian StyleFilippos Vallianatos; Georgios Michas. 2020. "Complexity of Fracturing in Terms of Non-Extensive Statistical Physics: From Earthquake Faults to Arctic Sea Ice Fracturing." Entropy 22, no. 11: 1194.
The unique physicochemical, electrical, mechanical, and thermal properties of micas make them suitable for a wide range of industrial applications, and thus, the interest for these kind of hydrous aluminosilicate minerals is still persistent, not only from a practical but also from a scientific point of view. In the present work, complex impedance spectroscopy measurements were carried out in muscovite and biotite micas, perpendicular to their cleavage planes, over a broad range of frequencies (10−2 Hz to 106 Hz) and temperatures (473–1173 K) that have not been measured so far. Different formalisms of data representation were used, namely, Cole-Cole plots of complex impedance, complex electrical conductivity and electric modulus to analyze the electrical behavior of micas and the electrical signatures of the dehydration/dehydroxylation processes. Our results suggest that ac-conductivity is affected by the structural hydroxyls and the different concentrations of transition metals (Fe, Ti and Mg) in biotite and muscovite micas. The estimated activation energies, i.e., 0.33–0.83 eV for biotite and 0.69–1.92 eV for muscovite, were attributed to proton and small polaron conduction, due to the bound water and different oxidation states of Fe.
Vassilios Saltas; Despoina Pentari; Filippos Vallianatos. Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study. Materials 2020, 13, 3513 .
AMA StyleVassilios Saltas, Despoina Pentari, Filippos Vallianatos. Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study. Materials. 2020; 13 (16):3513.
Chicago/Turabian StyleVassilios Saltas; Despoina Pentari; Filippos Vallianatos. 2020. "Complex Electrical Conductivity of Biotite and Muscovite Micas at Elevated Temperatures: A Comparative Study." Materials 13, no. 16: 3513.
The Polyphyto Dam, with a maximum water depth of 95 m and maximum water volume of ~ 1220 × 106 m3, is a medium-sized reservoir established on the Aliakmonas river (North Greece) in 1974. Although the broader area was considered as low seismic risk, a strong and damaging earthquake of magnitude (Mw) 6.6 occurred on May 13, 1995. In the present work, we investigate whether the recent seismicity in the vicinity of the Polyphyto Dam is associated with the water level fluctuations of the filled reservoir. To evaluate possible correlations and the occurrence of reservoir-triggered seismicity, we perform a cross-correlation analysis between the water level fluctuations of the reservoir and the observed regional seismicity rates, on datasets that span more than two decades, particularly for the period 1996–2017. The results of the analysis indicate that increased regional seismicity and moderate-sized events occur in the area at a lag of ~ 1 to 2 months after the water level maxima of the reservoir. This case of delayed seismicity is in accordance with a pore-pressure diffusion mechanism that decreases the effective normal stress along critically stressed fault zones, triggering the observed seismicity. Based on this mechanism, we estimate the hydraulic diffusivity and permeability of the regional fracture network and discuss the associated seismic hazard in the area.
Georgios Michas; Kyriaki Pavlou; Filippos Vallianatos; George Drakatos. Correlation Between Seismicity and Water Level Fluctuations in the Polyphyto Dam, North Greece. Pure and Applied Geophysics 2020, 177, 3851 -3870.
AMA StyleGeorgios Michas, Kyriaki Pavlou, Filippos Vallianatos, George Drakatos. Correlation Between Seismicity and Water Level Fluctuations in the Polyphyto Dam, North Greece. Pure and Applied Geophysics. 2020; 177 (8):3851-3870.
Chicago/Turabian StyleGeorgios Michas; Kyriaki Pavlou; Filippos Vallianatos; George Drakatos. 2020. "Correlation Between Seismicity and Water Level Fluctuations in the Polyphyto Dam, North Greece." Pure and Applied Geophysics 177, no. 8: 3851-3870.
In this paper, we present the recent progress in the experimental studies of the electrical conductivity of dominant nominally anhydrous minerals in the upper mantle and mantle transition zone of Earth, namely, olivine, pyroxene, garnet, wadsleyite and ringwoodite. The main influence factors, such as temperature, pressure, water content, oxygen fugacity, and anisotropy are discussed in detail. The dominant conduction mechanisms of Fe-bearing silicate minerals involve the iron-related small polaron with a relatively large activation enthalpy and the hydrogen-related defect with lower activation enthalpy. Specifically, we mainly focus on the variation of oxygen fugacity on the electrical conductivity of anhydrous and hydrous mantle minerals, which exhibit clearly different charge transport processes. In representative temperature and pressure environments, the hydrogen of nominally anhydrous minerals can tremendously enhance the electrical conductivity of the upper mantle and transition zone, and the influence of trace structural water (or hydrogen) is substantial. In combination with the geophysical data of magnetotelluric surveys, the laboratory-based electrical conductivity measurements can provide significant constraints to the water distribution in Earth’s interior.
Lidong Dai; Haiying Hu; Jianjun Jiang; Wenqing Sun; Heping Li; Mengqi Wang; Filippos Vallianatos; Vassilios Saltas. An Overview of the Experimental Studies on the Electrical Conductivity of Major Minerals in the Upper Mantle and Transition Zone. Materials 2020, 13, 408 .
AMA StyleLidong Dai, Haiying Hu, Jianjun Jiang, Wenqing Sun, Heping Li, Mengqi Wang, Filippos Vallianatos, Vassilios Saltas. An Overview of the Experimental Studies on the Electrical Conductivity of Major Minerals in the Upper Mantle and Transition Zone. Materials. 2020; 13 (2):408.
Chicago/Turabian StyleLidong Dai; Haiying Hu; Jianjun Jiang; Wenqing Sun; Heping Li; Mengqi Wang; Filippos Vallianatos; Vassilios Saltas. 2020. "An Overview of the Experimental Studies on the Electrical Conductivity of Major Minerals in the Upper Mantle and Transition Zone." Materials 13, no. 2: 408.
The drainage basins of Greece are analyzed in terms of hierarchy and discussed in view of Tsallis Entropy. This concept has been successfully used in a variety of complex systems, where fractality, memory and long-range interactions are dominant. The analysis indicates that the statistical distribution of drainage basins’ area in Greece, presents a hierarchical pattern that can be viewed within the frame of non-extensive statistical physics. Our work was based on the analysis of the ASTER GDEM v2 Digital Elevation Model of Greece, which offers a 30 m resolution, creating an accurate drainage basins’ database. Analyzing the drainage size (e.g., drainage basin area)-frequency distribution we discuss the connection of the observed power law exponents with the Tsallis entropic parameters, demonstrating the hierarchy observed in drainage areas for the set created for all over Greece and the subsets of drainages in the internal and external Hellenides that are the main tectonic structures in Greece. Furthermore, we discuss in terms of Tsallis entropy, the hierarchical patterns observed when the drainages are classified according to their relief or the Topographic Position Index (TPI). The deviation of distribution from power law for large drainages area is discussed.
Filippos Vallianatos; Maria Kouli. Evidence of Hierarchy in the Drainage Basins Size Distribution of Greece Derived from ASTER GDEM-v2 Data. Applied Sciences 2019, 10, 248 .
AMA StyleFilippos Vallianatos, Maria Kouli. Evidence of Hierarchy in the Drainage Basins Size Distribution of Greece Derived from ASTER GDEM-v2 Data. Applied Sciences. 2019; 10 (1):248.
Chicago/Turabian StyleFilippos Vallianatos; Maria Kouli. 2019. "Evidence of Hierarchy in the Drainage Basins Size Distribution of Greece Derived from ASTER GDEM-v2 Data." Applied Sciences 10, no. 1: 248.