Τίτλος:
Fractal evolution of MHz electromagnetic signals prior to earthquakes: results collected in Greece during 2009
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
This paper addressed a fractal evolution of 11 one-month lasting MHz electromagnetic disturbances, recorded in Greece prior to nine significant earthquakes of 2009. Time-space wavelet-based power spectral techniques were employed in the analysis. All investigated signals evolved naturally to epochs of fractal organization in space and time. Continuous organization was detected in seven signals. Significant number of successive (Formula presented.) power-law (Formula presented.) -values were observed lying between 1.5 and 3.0 or above. The majority of fractal segments exhibited anti-persistent (Formula presented.) or persistent (Formula presented.) behaviour. Switching between persistency and anti-persistency was also found. Locality and sensitivity were traced. Findings were considered indicative of self-organized critical states of the last stages of preparation of the investigated earthquakes. Results implied fractional Brownian modelling. Explanations were proposed in view of the asperity model. Persistent–anti-persistent MHz anomalies were due to self-organized micro-cracking of the heterogeneous medium of the earth's crust which may have led the system's evolution towards global failure. The precursory value of the signals was discussed. © 2014 Taylor & Francis.
Συγγραφείς:
Petraki, E.
Nikolopoulos, D.
Chaldeos, Y.
Koulouras, G.
Nomicos, C.
Yannakopoulos, P.H.
Kottou, S.
Stonham, J.
Περιοδικό:
Geomatics, Natural Hazards and Risk
Εκδότης:
Taylor and Francis Ltd.
Λέξεις-κλειδιά:
Fractals; Geophysics; Structural geology; Wavelet analysis, Asperity model; Electromagnetic disturbances; Electromagnetic signals; Global failure; Heterogeneous medium; Power spectral; Self-organized critical; Space and time, Earthquakes
DOI:
10.1080/19475705.2014.945496
