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Investigation of seismicity after the initiation of a Seismic Electric Signal activity until the main shock.

Sarlis NV, Skordas ES, Lazaridou MS, Varotsos PA - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2008)

Bottom Line: In the present work, analysing the time series of small earthquakes, the concept of natural time chi was used and the results revealed that the approach to criticality itself can be manifested by the probability density function (PDF) of kappa(1) calculated over an appropriate statistical ensemble.Here, kappa(1) is the variance kappa(1)(=<chi(2)>-<chi>(2)) resulting from the power spectrum of a function defined as Phi(omega)= summation operator(k=1)(N) p(k) exp(iomegachi(k)), where p(k) is the normalized energy of the k-th small earthquake and omega the natural frequency.Examples are presented, referring to the magnitude 6 approximately 7 class earthquakes that occurred in Greece.

View Article: PubMed Central - PubMed

Affiliation: Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens, Athens, Greece.

ABSTRACT
The behavior of seismicity in the area candidate to suffer a main shock is investigated after the observation of the Seismic Electric Signal activity until the impending main shock. This is based on the view that the occurrence of earthquakes is a critical phenomenon to which statistical dynamics may be applied. In the present work, analysing the time series of small earthquakes, the concept of natural time chi was used and the results revealed that the approach to criticality itself can be manifested by the probability density function (PDF) of kappa(1) calculated over an appropriate statistical ensemble. Here, kappa(1) is the variance kappa(1)(=-(2)) resulting from the power spectrum of a function defined as Phi(omega)= summation operator(k=1)(N) p(k) exp(iomegachi(k)), where p(k) is the normalized energy of the k-th small earthquake and omega the natural frequency. This PDF exhibits a maximum at kappa(1) asymptotically equal to 0.070 a few days before the main shock. Examples are presented, referring to the magnitude 6 approximately 7 class earthquakes that occurred in Greece.

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Related in: MedlinePlus

The same as Fig. 4, but for the area  after the SES activity at PIR on Jan. 14, 2008.
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f6-331: The same as Fig. 4, but for the area after the SES activity at PIR on Jan. 14, 2008.

Mentions: When the first SES activity was recorded on Jan. 14, 2008 at PIR (Fig. 2(c)), the study of the seismicity was immediately started in the area A, i.e., PIR selectivity map area as indicated in Ref. 40). Almost one week later, a long duration SES activity of the same polarity and amplitude was recorded also at PIR (Fig. 3(a)). The results of the computation are depicted in Fig. 6 (Mthres = 3.2), which reveals that Prob(κ1) also exhibits a clear bimodal feature, one mode of which maximizes at κ1 ≈ 0.070 upon the occurrence of a small event at 04:07 UT on Feb. 12, 2008 (shown by an arrow). Almost two days later, i.e., at 10:09 UT on Feb. 14, 2008, a major EQ of magnitude 6.7 occurred at 36.5°N 21.8°E, i.e., inside the area A shown by the rectangle with broken lines in Fig. 8. This EQ—according to USGS catalogue (which reported Mw6.9)—is the strongest EQ that occurred in Greek area during the last twenty five years. A few hours later, i.e., at 12:08 UT, a M6.6 EQ, which could have been an aftershock, occurred at 36.2°N 21.8°E. The bimodal feature in Fig. 6 might also be related to the occurrence of the two large EQs, but the mechanism is unclear. In addition, because there were two major SES activities in the month of January, i.e., before the two major Feb. 14 EQs, there is a possibility that the occurrence of these two large EQs might have been related with the appearance of these two SES activities. In fact, it might even be more proper to regard the two SES activities and two large EQs, occurring in a short span of time and space, as representing a single episode of SES activity and correlated seismic activity.


Investigation of seismicity after the initiation of a Seismic Electric Signal activity until the main shock.

Sarlis NV, Skordas ES, Lazaridou MS, Varotsos PA - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2008)

The same as Fig. 4, but for the area  after the SES activity at PIR on Jan. 14, 2008.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722020&req=5

f6-331: The same as Fig. 4, but for the area after the SES activity at PIR on Jan. 14, 2008.
Mentions: When the first SES activity was recorded on Jan. 14, 2008 at PIR (Fig. 2(c)), the study of the seismicity was immediately started in the area A, i.e., PIR selectivity map area as indicated in Ref. 40). Almost one week later, a long duration SES activity of the same polarity and amplitude was recorded also at PIR (Fig. 3(a)). The results of the computation are depicted in Fig. 6 (Mthres = 3.2), which reveals that Prob(κ1) also exhibits a clear bimodal feature, one mode of which maximizes at κ1 ≈ 0.070 upon the occurrence of a small event at 04:07 UT on Feb. 12, 2008 (shown by an arrow). Almost two days later, i.e., at 10:09 UT on Feb. 14, 2008, a major EQ of magnitude 6.7 occurred at 36.5°N 21.8°E, i.e., inside the area A shown by the rectangle with broken lines in Fig. 8. This EQ—according to USGS catalogue (which reported Mw6.9)—is the strongest EQ that occurred in Greek area during the last twenty five years. A few hours later, i.e., at 12:08 UT, a M6.6 EQ, which could have been an aftershock, occurred at 36.2°N 21.8°E. The bimodal feature in Fig. 6 might also be related to the occurrence of the two large EQs, but the mechanism is unclear. In addition, because there were two major SES activities in the month of January, i.e., before the two major Feb. 14 EQs, there is a possibility that the occurrence of these two large EQs might have been related with the appearance of these two SES activities. In fact, it might even be more proper to regard the two SES activities and two large EQs, occurring in a short span of time and space, as representing a single episode of SES activity and correlated seismic activity.

Bottom Line: In the present work, analysing the time series of small earthquakes, the concept of natural time chi was used and the results revealed that the approach to criticality itself can be manifested by the probability density function (PDF) of kappa(1) calculated over an appropriate statistical ensemble.Here, kappa(1) is the variance kappa(1)(=<chi(2)>-<chi>(2)) resulting from the power spectrum of a function defined as Phi(omega)= summation operator(k=1)(N) p(k) exp(iomegachi(k)), where p(k) is the normalized energy of the k-th small earthquake and omega the natural frequency.Examples are presented, referring to the magnitude 6 approximately 7 class earthquakes that occurred in Greece.

View Article: PubMed Central - PubMed

Affiliation: Solid State Section and Solid Earth Physics Institute, Physics Department, University of Athens, Athens, Greece.

ABSTRACT
The behavior of seismicity in the area candidate to suffer a main shock is investigated after the observation of the Seismic Electric Signal activity until the impending main shock. This is based on the view that the occurrence of earthquakes is a critical phenomenon to which statistical dynamics may be applied. In the present work, analysing the time series of small earthquakes, the concept of natural time chi was used and the results revealed that the approach to criticality itself can be manifested by the probability density function (PDF) of kappa(1) calculated over an appropriate statistical ensemble. Here, kappa(1) is the variance kappa(1)(=-(2)) resulting from the power spectrum of a function defined as Phi(omega)= summation operator(k=1)(N) p(k) exp(iomegachi(k)), where p(k) is the normalized energy of the k-th small earthquake and omega the natural frequency. This PDF exhibits a maximum at kappa(1) asymptotically equal to 0.070 a few days before the main shock. Examples are presented, referring to the magnitude 6 approximately 7 class earthquakes that occurred in Greece.

Show MeSH
Related in: MedlinePlus