| Recent results [1,2] have been published on the basis of the analysis of seismicity of
Japan in a new time domain -termed natural time [3] -which reveals some dynamic
features hidden in the time series of complex systems [4]. These recent results are as
follows:
First, Varotsos et al. [1] identified that the fluctuations of the order parameter of
seismicity defined in natural time [5] exhibited a clearly detectable minimum approximately
at the time of the initiation of the pronounced Seismic Electric Signals (SES) activity
observed by Uyeda et al.[6,7] almost two months before the onset of the volcanic-seismic
swarm activity in 2000 in the Izu Island region, Japan. These two phenomena were
found to be also linked in space, which is discussed in the frame of earthquake
networks. SES are low frequency (-¤ 1Hz) changes of the electric field of the Earth
that have been found in Greece [8-11] and Japan [6,12,13] to precede earthquakes
with lead times ranging from several hours to a few months. They are emitted [14]
from the focal area when the stress reaches a critical value before the earthquake
occurrence.
Second, Sarlis et al. [2] proceeded to the analysis of the Japan seismic catalog in
natural time from 1 January 1984 to 11 March 2011 (the day of the occurrence
of the Mw9.0 Tohoku earthquake) and showed that the fluctuations of the order
parameter of seismicity exhibits distinct minima a few months before all the shallow
earthquakes of magnitude 7.6 or larger during this 27 year period in Japanese area.
Among these minima, the deepest one was observed before the Mw9.0 Tohoku
earthquake on ~ 5 January 2011. This fact, in view of the aforementioned findings of
Varotsos et al. [1], reflects that a strong SES activity should have been initiated on the
same date, i.e., on ~5 January 2011. This SES activity should be accompanied
[15] by magnetic field variations mainly on the Z component [16], which has been
recently verified by Xu et al. [17] who reported that anomalous variations of the
geomagnetic field have been observed mainly in the vertical component for about 10 days
(4 to 14 January 2011), i.e., approximately 2 months before the Mw9.0 Tohoku
earthquake.
[1] P. A. Varotsos, N. V. Sarlis, E. S. Skordas, and M. S. Lazaridou, Tectonophysics 589,
116 (2013).
[2] N. V. Sarlis, E. S. Skordas, P. A. Varotsos, T. Nagao, M. Kamogawa, H. Tanaka, and
S. Uyeda, Proc. Natl. Acad. Sci. USA 110, 13734 (2013).
[3] P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, Phys. Rev. E 66, 011902
(2002).
[4] P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, Natural Time Analysis: The new view
of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series
(Springer- Verlag, Berlin Heidelberg, 2011).
[5] P. A. Varotsos, N. V. Sarlis, H. K. Tanaka, and E. S. Skordas, Phys. Rev. E 72, 041103
(2005).
[6] S. Uyeda, M. Hayakawa, T. Nagao, O. Molchanov, K. Hattori, Y. Orihara, K. Gotoh,
Y. Akinaga, and H. Tanaka, Proc. Natl. Acad. Sci. USA 99, 7352 (2002).
[7] S. Uyeda, M. Kamogawa, and H. Tanaka, J. Geophys. Res. 114, B02310
(2009).
[8] P. Varotsos and K. Alexopoulos, Tectonophysics 110, 73 (1984).
[9] P. Varotsos and K. Alexopoulos, Tectonophysics 110, 99 (1984).
[10] P. Varotsos and M. Lazaridou, Tectonophysics 188, 321 (1991).
[11] P. Varotsos, K. Alexopoulos, and M. Lazaridou, Tectonophysics 224, 1
(1993).
[12] S. Uyeda, T. Nagao, Y. Orihara, T. Yamaguchi, and I. Takahashi, Proc. Natl. Acad.
Sci. USA 97, 4561 (2000).
[13] Y. Orihara, M. Kamogawa, T. Nagao, and S. Uyeda, Proc. Natl. Acad. Sci. USA 109,
19125 (2012).
[14] P. Varotsos and K. Alexopoulos, Thermodynamics of Point Defects and their
Relation with Bulk Properties (North Holland, Amsterdam, 1986).
[15] P. V. Varotsos, N. V. Sarlis, and E. S. Skordas, Phys. Rev. Lett. 91, 148501
(2003).
[16] N. Sarlis and P. Varotsos, J. Geodynamics 33, 463 (2002).
[17] G. Xu, P. Han, Q. Huang, K. Hattori, F. Febriani, and H. Yamaguchi, J. Asian Earth
Sci. 77, 59 (2013). |