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            W9 Tohoku earthquake in 2011 in Japan: precursors uncovered by natural time analysis

By analyzing the seismicity in the new time domain termed natural time [1],&#160; the entropy changes of seismicity before major earthquakes have been studied. It was found [2-5] that the key quantity is the entropy change &#916;S under time reversal, which is minimized a few months before major earthquakes such as the M9.0 Tohoku earthquake [2] on 11 March 2011 and the M8.2 Chiapas earthquake [3] in Mexico on 7 September 2017; accompanied by an abrupt increase of its fluctuations [4,5]. Here we discuss how these fluctuations may lead to a procedure through which the occurrence time of an impending mainshock can be estimated [6].References1. Varotsos P.A., Sarlis N.V. and Skordas E.S., Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series (Springer-Verlag, Berlin Heidelberg) 2011.2. N. V. Sarlis, E. S. Skordas, and P. A. Varotsos, "A remarkable change of the entropy of seismicity in natural time under time reversal before the super-giant M9 Tohoku earthquake on 11 March 2011", EPL (Europhysics Letters), 124 (2018), 29001.3. N. V. Sarlis, E. S. Skordas P. A. Varotsos, A. Ram&#237;rez-Rojas, E. L. Flores-M&#225;rquez, "Natural time analysis: On the deadly Mexico M8.2 earthquake on 7 September 2017", Physica A 506 (2018), 625-634.4. P. A. Varotsos, N. V. Sarlis and E. S. Skordas, "Tsallis Entropy Index q and the Complexity Measure of Seismicity in Natural Time under Time Reversal before the M9 Tohoku Earthquake in 2011", Entropy 20 (2018), 757.5. A. Ram&#237;rez-Rojas, E. L. Flores-M&#225;rquez, N. V. Sarlis and P. A. Varotsos, "The Complexity Measures Associated with the Fluctuations of the Entropy in Natural Time before the Deadly M&#233;xico M8.2 Earthquake on 7 September 2017", Entropy 20 (2018), 477.6. E. S. Skordas, N. V. Sarlis and P. A. Varotsos &#8220;Identifying the occurrence time of an impending major earthquake by means of the fluctuations of the entropy change under time reversal&#8221;, EPL (Europhysics Letters), in press.

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Remote sensing natural time analysis of heartbeat data by means of a portable photoplethysmography device

International Journal of Remote Sensing ◽

10.1080/2150704x.2020.1847351 ◽

2020 ◽

Vol 42 (6) ◽

pp. 2292-2302

Author(s):

G. Baldoumas ◽

D. Peschos ◽

G. Tatsis ◽

V. Christofilakis ◽

S. K. Chronopoulos ◽

...

Keyword(s):

Remote Sensing ◽

Time Analysis ◽

Natural Time ◽

Natural Time Analysis

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Natural-time analysis of critical phenomena: The case of seismicity

EPL (Europhysics Letters) ◽

10.1209/0295-5075/92/29002 ◽

2010 ◽

Vol 92 (2) ◽

pp. 29002 ◽

Cited By ~ 25

Author(s):

P. A. Varotsos ◽

N. V. Sarlis ◽

E. S. Skordas ◽

S. Uyeda ◽

M. Kamogawa

Keyword(s):

Critical Phenomena ◽

Time Analysis ◽

Natural Time ◽

Natural Time Analysis

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Natural Time Analysis of Seismic Time Series

Complexity of Seismic Time Series ◽

10.1016/b978-0-12-813138-1.00007-9 ◽

2018 ◽

pp. 199-235 ◽

Cited By ~ 1

Author(s):

Nicholas V. Sarlis ◽

Efthimios S. Skordas ◽

Panayiotis A. Varotsos

Keyword(s):

Time Series ◽

Time Analysis ◽

Natural Time ◽

Natural Time Analysis

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Natural Time Analysis: The Area under the Receiver Operating Characteristic Curve of the Order Parameter Fluctuations Minima Preceding Major Earthquakes

Entropy ◽

10.3390/e22050583 ◽

2020 ◽

Vol 22 (5) ◽

pp. 583 ◽

Cited By ~ 5

Author(s):

Nicholas V. Sarlis ◽

Efthimios S. Skordas ◽

Stavros-Richard G. Christopoulos ◽

Panayiotis A. Varotsos

Keyword(s):

Order Parameter ◽

Characteristic Curve ◽

Activity Patterns ◽

Space Physics ◽

Operating Characteristics ◽

Time Analysis ◽

Natural Time ◽

Natural Time Analysis ◽

Electric Signals ◽

Receiver Operating

It has been reported that major earthquakes are preceded by Seismic Electric Signals (SES). Observations show that in the natural time analysis of an earthquake (EQ) catalog, an SES activity starts when the fluctuations of the order parameter of seismicity exhibit a minimum. Fifteen distinct minima—observed simultaneously at two different natural time scales and deeper than a certain threshold—are found on analyzing the seismicity of Japan from 1 January 1984 to 11 March 2011 (the time of the M9 Tohoku EQ occurrence) 1 to 3 months before large EQs. Six (out of 15) of these minima preceded all shallow EQs of magnitude 7.6 or larger, while nine are followed by smaller EQs. The latter false positives can be excluded by a proper procedure (J. Geophys. Res. Space Physics 2014, 119, 9192–9206) that considers aspects of EQ networks based on similar activity patterns. These results are studied here by means of the receiver operating characteristics (ROC) technique by focusing on the area under the ROC curve (AUC). If this area, which is currently considered an effective way to summarize the overall diagnostic accuracy of a test, has the value 1, it corresponds to a perfectly accurate test. Here, we find that the AUC is around 0.95 which is evaluated as outstanding.

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A Prototype Photoplethysmography Electronic Device that Distinguishes Congestive Heart Failure from Healthy Individuals by Applying Natural Time Analysis

Electronics ◽

10.3390/electronics8111288 ◽

2019 ◽

Vol 8 (11) ◽

pp. 1288 ◽

Cited By ~ 11

Author(s):

George Baldoumas ◽

Dimitrios Peschos ◽

Giorgos Tatsis ◽

Spyridon K. Chronopoulos ◽

Vasilis Christofilakis ◽

...

Keyword(s):

Heart Failure ◽

Congestive Heart Failure ◽

Electronic Device ◽

Low Cost ◽

Prototype System ◽

Healthy Individuals ◽

Time Analysis ◽

Clear Separation ◽

Natural Time ◽

Natural Time Analysis

In this paper, a prototype photoplethysmography (PPG) electronic device is presented for the distinction of individuals with congestive heart failure (CHF) from the healthy (H) by applying the concept of Natural Time Analysis (NTA). Data were collected simultaneously with a conventional three-electrode electrocardiography (ECG) system and our prototype PPG electronic device from H and CHF volunteers at the 2nd Department of Cardiology, Medical School of Ioannina, Greece. Statistical analysis of the results show a clear separation of CHF from H subjects by means of NTA for both the conventional ECG system and our PPG prototype system, with a clearly better distinction for the second one which additionally inherits the advantages of a low-cost portable device.

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