Abstract
Abstract. A number of Seismic Electric signals data have been accumulated during the last two decades that also includes the signals observed before the magnitude 6 class earthquakes that occurred in Greece very recently i.e., the first two months of 2008. Using all the available data we investigate whether a possible interconnection exists between the lead time of Seismic Electric Signals and the stress drop of subsequent earthquakes. We show that for "non thrust" earthquakes a power law relation emerges with an exponent value around 0.29, the possible physical meaning of which is discussed. This value is very close to the range of critical exponents that govern the fracture processes and is also comparable with the value of the slope, found much earlier by the VAN group, in the linear relation between the logarithm of the SES amplitude and the earthquake magnitude.
Highlights
There is a tendency to consider that electromagnetic phenomena related to earthquake preparation processes in the highly heterogeneous crust should be described by “non linear” models which obey power laws and have fractal geometry (Varotsos, 2005)
We found 12 earthquakes with reported Brune’s stress drop values derived from teleseismic body waves spectra (Papazachos et al, 1988; Stavrakakis and Blionas, 1990; Chouliaras and Stavrakakis, 1997; Stavrakakis et al, 2002; Benetatos et al, 2002; Papadimitriou, personal communication, 2007, 2008) and two earthquakes with reported fault dimensions and seismic moments (Kiratzi et al, 1985)
Sornette et al (1989) attempted a physical insight of the value of this slope by interconnecting it with critical exponents emerged in the crack percolation theory
Summary
There is a tendency to consider that electromagnetic phenomena related to earthquake preparation processes in the highly heterogeneous crust should be described by “non linear” models which obey power laws and have fractal geometry (Varotsos, 2005). The scope of the present paper is to treat pre-seismic electromagnetic signals and associated earthquakes within the framework of “critical point” theories and to investigate possible power law relationships with fractal critical exponents between their parameters. Some interesting characteristics of the SES signals (Varotsos and Alexopoulos, 1984a, b, 1987; Varotsos et al, 1993) are: i) the lead time, t, which is the time difference between the SES detection and the earthquake occurrence and can vary from a few hours to a few months.
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