Identifying the occurrence time of an impending major earthquake: a review

Varotsos, P.; Sarlis, N. V.; Skordas, E. S.

doi:10.1007/s11589-017-0182-7

Cited by 33 publications

(38 citation statements)

References 55 publications

(61 reference statements)

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“…It is notable that the occurrence of the two EQs under study took place almost a week after the criticality condition κ 1 = 0.070 has been met for various magnitude thresholds. This compares favorably with the time window of a few days up to one week already found from various SES activities in Greece, Japan and United States [2,4,18,[36][37][38][39].…”

Section: Discussionsupporting

confidence: 78%

Natural Time Analysis: Results Related to Two Earthquakes in Greece during 2019

Sarlis

Skordas

Varotsos

2019

The 2nd International Electronic Conference on Geosciences

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The following two earthquakes occurred in Greece during 2019: First, a Mw5.4 earthquake close to Preveza city in Western Greece on 5 February and a Mw5.3 earthquake 50 km East of Patras on 30 March. Here, we present the natural time analysis of the Seismic Electric Signals (SES) activities that have been recorded before these two earthquakes. In addition, we explain how the occurrence times of these two earthquakes can be identified by analyzing in natural time the seismicity subsequent to the SES activities.

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Section: Discussionsupporting

confidence: 78%

Natural Time Analysis: Results Related to Two Earthquakes in Greece during 2019

Sarlis

Skordas

Varotsos

2019

The 2nd International Electronic Conference on Geosciences

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“…This is observed in Figures 2-7. This is a significant finding that has been acknowledged by numerous investigators [40][41][42][43][44][45][46][47]61,64,[70][71][72]74,[85][86][87][88][89][90]. As extensively discussed in the above publications, the employed methods reveal hidden patterns in the time series, and for this reason their time evolution is different from that of the time series.…”

Section: Time Series (Subfigures (A) Of Figures 2-7)mentioning

confidence: 88%

Fractal and Long-Memory Traces in PM10 Time Series in Athens, Greece

et al. 2019

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This work examines if chaos and long memory exist in PM 10 concentrations recorded in Athens, Greece. The algorithms of Katz, Higuchi, and Sevcik were employed for the calculation of fractal dimensions and Rescaled Range (R/S) analysis for the calculation of the Hurst exponent. Windows of approximately two months' duration were employed, sliding one sample forward until the end of each utilized signal. Analysis was applied to three long PM 10 time series recorded by three different stations located around Athens. Analysis identified numerous dynamical complex fractal time-series segments with patterns of long memory. All these windows exhibited Hurst exponents above 0.8 and fractal dimensions below 1.5 for the Katz and Higuchi algorithms, and 1.2 for the Sevcik algorithm. The paper discusses the importance of threshold values for the postanalysis of the discrimination of fractal and long-memory windows. After setting thresholds, computational calculations were performed on all possible combinations of two or more techniques for the data of all or two stations under study. When all techniques were combined, several common dates were found for the data of the two combinations of two stations. When the three techniques were combined, more common dates were found if the Katz algorithm was not included in the meta-analysis. Excluding Katz's algorithm, 12 common dates were found for the data from all stations. This is the first time that the results from sliding-window chaos and long-memory techniques in PM 10 time series were combined in this manner.

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“…The extent of the usefulness of this result for the case of the M W 9 Tohoku EQ in 2011 and in particular for the determination of its occurrence time has been recently investigated by Varotsos et al (2017). They reviewed, in the light of the recent advances, the procedure to identify the occurrence time which in general is achieved by computing the j 1 values of the seismicity occurring in the candidate epicentral area after the initiation of the SES activity.…”

Section: Discussionmentioning

confidence: 99%

“…They reviewed, in the light of the recent advances, the procedure to identify the occurrence time which in general is achieved by computing the j 1 values of the seismicity occurring in the candidate epicentral area after the initiation of the SES activity. Along these lines, for the case of the M W 9 Tohoku EQ, Varotsos et al (2017) computed the j 1 values of seismicity in the epicentral area estimated in Sarlis et al (2015) by starting this computation from January 5, 2011, since it is the date of the appearance of the deepest minimum b W,min , which was found to be simultaneous )-as mentioned above-with the anomalous geomagnetic field variations and hence with strong SES activity. The results of this computation showed that the condition j 1 = 0.070 (which signals that the mainshock is going to occur within a few days or so) was fulfilled almost one day before the Tohoku EQ (Varotsos et al 2017).…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2017

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This paper reviews the precursory phenomena of the 2011 M W 9 Tohoku earthquake in Japan that emerge solely when we analyze the seismicity data in a new time domain termed natural time. If we do not consider this analysis, important precursory changes cannot be identified and hence are missed. Natural time analysis has the privilege that enables the introduction of an order parameter of seismicity. In this frame, we find that the fluctuations of this parameter exhibit an unprecedented characteristic change, i.e., an evident minimum, approximately two months before Tohoku earthquake, which strikingly is almost simultaneous with unique anomalous geomagnetic field variations recorded mainly on the z component. This is consistent with our finding that such a characteristic change in seismicity appears when a seismic electric signal (SES) activity of the VAN method (from the initials of Varotsos, Alexopoulos, Nomicos) initiates, and provides a direct confirmation of the physical interconnection between SES and seismicity.

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Identifying the occurrence time of an impending major earthquake: a review

Cited by 33 publications

References 55 publications

Natural Time Analysis: Results Related to Two Earthquakes in Greece during 2019

Natural Time Analysis: Results Related to Two Earthquakes in Greece during 2019

Fractal and Long-Memory Traces in PM10 Time Series in Athens, Greece

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

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