scholarly journals Analysis of electrical activity and seismicity in the natural time domain for the volcanic-seismic swarm activity in 2000 in the Izu Island region, Japan

2009 ◽  
Vol 114 (B2) ◽  
Author(s):  
S. Uyeda ◽  
M. Kamogawa ◽  
H. Tanaka
Keyword(s):  
Electrical Activity ◽  
Time Domain ◽  
Island Region ◽  
Seismic Swarm ◽  
Natural Time ◽  
Swarm Activity

METHODS TO QUANTITATE ATRIAL ELECTRICAL ACTIVITY USING ELECTROGRAMS ACQUIRED DURING ATRIAL FIBRILLATION

2014 ◽  
Vol 26 (06) ◽  
pp. 1430001
Author(s):  
Edward J. Ciaccio ◽  
Angelo B. Biviano ◽  
Hasan Garan
Keyword(s):  
Atrial Fibrillation ◽  
Electrical Activity ◽  
Frequency Domain ◽  
Time Domain ◽  
Periodic Pattern ◽  
Spectral Parameters ◽  
Domain Method ◽  
Frequency Domain Methods ◽  
Atrial Electrograms ◽  
Fractionated Electrograms

Herein, commonly used quantitative bioengineering methods that have been developed to analyze fractionated electrograms recorded from the surface of the atria during atrial fibrillation (AF) are described. Techniques were categorized as time-domain and frequency-domain methods. The main time-domain method is peak counting. Its variations based on preprocessing and thresholding are discussed. The main frequency-domain method is spectral analysis. Two spectral estimators, the discrete Fourier transform (DFT) and the new spectral estimator (NSE) are described. The ability of each estimator to detect the main periodic component of fractionated atrial electrograms is compared. Several spectral parameters that are used for analysis of atrial electrograms including the dominant frequency (DF), dominant amplitude (DA) and mean spectral profile (MP) are defined. Mean values of these parameters are compared in paroxysmal versus persistent AF fractionated electrograms based upon the results of several studies. Time-domain methods are shown to work best for analysis with deterministic, not fractionated atrial electrograms. For fractionated atrial electrograms, frequency-domain methods are often used. The DF, DA and MP spectral parameters are significantly different in paroxysmal versus longstanding persistent AF recordings. The DF and the DA are significantly higher, and the MP is significantly lower, in persistent AF electrogram recordings. The higher DF and DA parameter values reflect substrate remodeling in persistent AF, which increases the stability of the electrical activation pattern. The lower MP value in persistent AF reflects the lower spectral noise floor, indicative of a less complex and more periodic pattern of electrical activity.

scholarly journals Entropy in the natural time domain

2004 ◽  
Vol 70 (1) ◽  
Author(s):  
P. A. Varotsos ◽  
N. V. Sarlis ◽  
E. S. Skordas ◽  
M. S. Lazaridou
Keyword(s):  
Time Domain ◽  
Natural Time

scholarly journals A plausible universal behaviour of earthquakes in the natural time-domain

2004 ◽  
Vol 80 (6) ◽  
pp. 283-289 ◽  
Author(s):  
Haruo TANAKA ◽  
Panayiotis A. VAROTSOS ◽  
Nicholas V. SARLIS ◽  
Efthimios S. SKORDAS
Keyword(s):  
Time Domain ◽  
Natural Time ◽  
Universal Behaviour

scholarly journals Entropy in Natural Time and the Associated Complexity Measures

2017 ◽  
Author(s):  
Nicholas V. Sarlis
Keyword(s):  
Complex System ◽  
Time Domain ◽  
Time Reversal ◽  
Southern Oscillation ◽  
Complexity Measures ◽  
Natural Time ◽  
Electric Signals ◽  
Atmospheric Phenomena ◽  
Analysis Of Time Series ◽  
New Time

Natural time is a new time domain introduced in 2001. The analysis of time series associated with a complex system in natural time may provide useful information and may reveal properties that are usually hidden when studying the system in conventional time. In this new time domain, an entropy has been defined and complexity measures based on this entropy as well as its value under time-reversal have been introduced and found applications in various complex systems. Here, we review these applications in the electric signals that precede rupture, e.g., earthquakes, in the analysis of electrocardiograms, as well as in global atmospheric phenomena like the El Nino/La Nina Southern Oscillation.

Patterns of seismic swarm activity in the Corinth Rift in 2000–2005

2011 ◽  
Vol 47 (7) ◽  
pp. 610-622 ◽  
Author(s):  
M. G. Potanina ◽  
V. B. Smirnov ◽  
P. Bernard
Keyword(s):  
Seismic Swarm ◽  
Swarm Activity

scholarly journals Detecting Criticality by Exploring the Acoustic Activity in Terms of the “Natural-Time” Concept

2021 ◽  
Vol 12 (1) ◽  
pp. 231
Author(s):  
Andronikos Loukidis ◽  
Dimos Triantis ◽  
Ilias Stavrakas ◽  
Ermioni D. Pasiou ◽  
Stavros K. Kourkoulis
Keyword(s):  
Power Law ◽  
Time Domain ◽  
Temporal Evolution ◽  
Critical Stage ◽  
Acoustic Activity ◽  
Natural Time ◽  
Self Consistent ◽  
Impending Fracture

The acoustic activity developed in marble specimens under various loading schemes is explored in terms of the recently introduced F-function. The novelty of the study is that instead of describing the temporal evolution of the F-function in terms of conventional time, the Natural Time concept is employed. Although completely different geometries and loading schemes were considered, the evolution of the F-function in the Natural Time domain exhibits a self-consistent motive: its values increase progressively with fluctuations of varying intensity, however, while the fracture is approaching, a power law appears to systematically govern the response of the specimen/structure loaded. The exponent of this law, somehow corresponding to the intensity of the acoustic activity within the loaded complex, varies within broad limits. The onset of validity of the power law designates that the system has entered into its critical stage, namely that of impending fracture, providing a useful pre-failure signal.

scholarly journals Entropy of geoelectrical time series in the natural time domain

2011 ◽  
Vol 11 (1) ◽  
pp. 219-225 ◽  
Author(s):  
A. Ramírez-Rojas ◽  
L. Telesca ◽  
F. Angulo-Brown
Keyword(s):  
Time Series ◽  
Time Domain ◽  
Chaotic Map ◽  
Low Frequency ◽  
Artificial Noise ◽  
Strong Earthquakes ◽  
Natural Time ◽  
Correlation Degree ◽  
Electric Signals ◽  
Simulated Time

Abstract. Seismic electric signals (SES) have been considered precursors of strong earthquakes, and, recently, their dynamics have been investigated within the Natural Time Domain (NTD) (Varotsos et al., 2004). In this paper we apply the NTD approach and the chaotic map signal analysis to two geoelectric time series recorded in a seismically very active area of Mexico, where two strong earthquakes, M=6.6 and M=7.4, occurred on 24 October 1993 and 14 September 1995, respectively. The low frequency geoelectric signals measured display periods with dichotomic behavior. Our findings point out to an increase of the correlation degree of the geoelectric signals before the occurrence of strong earthquakes; furthermore, the power spectrum and entropy in NTD are in good agreement with the results published in literature. Our results were validated by the analysis of a chaotic map simulated time series, which revealed the typical characteristics of artificial noise.

Sign in / Sign up

Export Citation Format

Share Document