alexa Long-Memory Trends in Disturbances of Radon in Soil Prior to the Twin ML=5.1 Earthquakes of 17 November 2014 Greece
Geology & Earth Science

Geology & Earth Science

Journal of Earth Science & Climatic Change

Author(s): Nikolopoulos D, Petraki E, Nomicos C, Koulouras G, Kottou S

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Radon is an alpha emitting noble gas that is produced by the radioactive decay of uranium (238U) series [1]. The most significant isotope is 222Rn because it's concentration is higher when compared to the trivial concentrations of the other radon isotopes [1]. 222Rn (hereafter, radon) has a relatively long half-life (3.8 days). For this reason it appears at measurable levels in the environment. As radon decays it may dissolve in soil’s pores and fluid [1]. Thereafter, it migrates near or far and dilutes in atmosphere, surface and underground water [1]. Anomalous radon variations have been observed prior to earthquakes in groundwater, soil gas, atmosphere and thermal spas [2-14]. It has been identified as a potential short-term [15] earthquake precursor. The related research is still in progress, investigating further potential associations between radon and earthquakes [2-14]. Nevertheless, no universal model exists to serve as a pre-earthquake signature [16,17]. Moreover, there is no definite rule to link any kind of pre-earthquake anomaly to a specific forthcoming seismic event, either if this is intense or mild [16-18]. For these reasons, despite the fairly abundant circumstantial evidence, the scientific community still debates the precursory value of premonitory anomalies detected prior to earthquakes [16]. On the other hand, well established criteria exist to identify pre-earthquake patterns hidden in time-series which are based on the concepts of fractality and self-organization [15-47]. Four recent reports revealed fractal Self-Organized Critical (SOC) characteristics of radon disorders prior to significant earthquakes in Greece [18- 21]. An important recent paper [22] reported also pre-earthquake fractal characteristics of a 3 year radon signal through the method of multifractal Detrended Fluctuation Analysis. The recent radon related papers [18-22] employed methods such as the wavelet spectral fractal analysis, the Detrended Fluctuation Analysis and the entropy analysis and reported that the investigated disorders exhibited self-affine persistent–antipersistent behavior similar to those of the pre-seismic electromagnetic disturbances of the ULF, LF and HF range [23-47]. This paper reports the anomalous radon signal that was collected by the telemetric radon station prior to the twin ML=5.1 earthquakes of 17 November 2014 that occurred in Greece. Trends of long-memory are searched through Rescaled Range (R/S) analysis [48,49] and Detrended Fluctuation Analysis (DFA) [50-56]. Results are interpreted in terms of Hurst exponents [48,49].

This article was published in Journal of Earth Science & Climatic Change and referenced in Journal of Earth Science & Climatic Change

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