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Download Download Research in Geophysics 2014; volume 4:5001 The ultra low frequency Introduction Correspondence: Gergios C. Anagnostopoulos, electromagnetic radiation Department of Electrical & Computer observed in the topside Although earthquakes (EQs) are known to Engineering, Democritus University of Thrace, be complex phenomena, there has been grow- Panepistimioupoli Kimmeria, Building B, 67100 ionosphere above boundaries Xanthi, Greece. of tectonic plates ing evidence in the last decades that EQs pre- Tel.: +30.25410.79986 - Fax: +30.25410.79590. cursory phenomena can be detected. This evi- E-mail: [email protected] dence was based on studies of certain effects 1,2 Michael A. Athanasiou, related to electric and magnetic fields, ionos- Key words: seismo-electromagnetic effects, 3 Gergios C. Anagnostopoulos, pheric perturbations, nightglow observations, Earth’s electromagnetic ultra low frequency radi- Constantinos N. David,2 electromagnetic (EM) emissions from direct ation, electromagnetic perturbations, seismic Gregorios G. Machairidis4 precursors, ionospheric, earthquake-related currents to high frequency range and radiation satellite observations. 1Department of Information & belt electron precipitation in the topside iono- 1-6 Communications, Technical University of sphere. Acknowledgments: the authors thank Dr Berthelier for providing the DEMETER/ICE data Serres, Serres; 2Department of During the preparation of earthquakes, many chemical materials emanate, such as and Dr M. Parrot for his comments on a part of Mechanical Engineering, Technical radon and metal aerosols. According to the the manuscript. University of Serres, Serres; 3Department lithosphere-atmospere-ionosphere coupling of Electrical & Computer Engineering, Funding: this study was supported by the NSRF (LAIC) model proposed by Pulinets and 2007-2013 Thales - Hellenic National Network for Democritus University of Thrace, Xanthi; 7 Ouzounov, the á-particles emitted by radon Space Weather Research (HNSWRN) - MIS 377274 4 Connect I.T., Informatics Company, are converted finally in heat, and cause enor- project of the Greek Ministry of Education, Lifelong Xanthi, Greece mous amounts of energy release after the con- Learning and Religious Affairs - General Secretariat densation/evaporation process. Pulinets5 fur- for Research and Technology and the Seismic nd ther elaborated the physical mechanisms Precursor Satellite Signals (2 Phase) Project of the Special Account of Democritus, University of 7 described by Pulinets and Ouzounov and Thrace. The financial support from the Research Abstract attempted to demonstrate the LAIC as a com- onlyCommittee of the Technical University (TEI) of plex system, being a derivative of the intensive Serres under grant 117/13/3.10.2012 is also grateful- ly acknowledged by the leading author. In this paper we present results of a compar- radon activity before earthquakes start to ison between ultra low frequency (ULF) elec- demonstrate anomalies in the atmosphere, ionosphere and magnetosphere at timesuse when Received for publication: 22 July 2013. tromagnetic (EM) radiation, recorded by an Revision received: 6 March 2014. the system approaches the critical state. On electric field instrument onboard the satellite Accepted for publication: 6 July 2014. the other hand, acoustic gravity waves are con- detection of electromagnetic emissions trans- sidered to be generated before and after an mitted from earthquake regions in the topside This work is licensed under a Creative Commons earthquake at the ground-atmosphere bound- Attribution NonCommercial 3.0 License (CC BY- ionosphere, and the seismicity of regions with ary.8 These waves propagate in the atmos- NC 3.0). high and low seismic activity. In particular, we phere, penetrate into the atmosphere, and evaluated the energy variations of the ULF Ez- ©Copyright M.A. Athanasiou et al., 2014 then disturb plasma parameters in the lower electric field component during a period of Licensee PAGEPress, Italy ionosphere.9 four years (2006-2009), in order to examine Research in Geophysics 2014; 4:5001 Theoretical studies and laboratory experi- the possible relation of ULF EM radiation with doi:10.4081/rg.2014.5001 ments suggest that deformations of rocks seismogenic regions located in Central under special pressure and temperature condi- America, Indonesia, the Eastern commercialtions exist in the brittle seismogenic crust, Mediterranean Basin and Greece. As a tool for which destabilise the mechanical and electri- rent, which generates EM signals. If the out- evaluating the ULF Ez energy variations we cal properties of the solids. In particular, flow occurs in bursts, it will lead to short EM used singular spectrum analysis techniques. according to the electromechanical mecha- pulses. If the outflow is continuous, the cur- The results of our analysis clearly show a sig- nism, electric charges are generated as the rents may fluctuate, generating EM emissions nificant increase of the ULF EM Nonenergy emit- result of friction and a piezoelectric phenome- over a wide frequency range. Numerical com- ted from regions of highest seismic activity at non that changes the Earth’s electric field and putations suggest that ULF/ELF electromagnet- the boundaries tectonic plates. Furthermore, generates EM waves, which are considered to ic emissions lower than 20 Hz can transverse 16 we found that higher electromagnetic radia- propagate to the upper atmosphere and iono- directly into the upper ionosphere. tion was detected in a region above the north- sphere.10-13 Indeed, from the 80’s until now, dozens of ern-western Greek Arc (R1) than above the The study on seismogenic ultra low frequen- studies regarding several seismic events have adjacent region including Athens and its urban cy (ULF) emissions started in the early 1990s. been presented validating the existence of EM area. We interpret these results of the present Even though the radio emissions are generat- wave emission during seismic activity.17,18 study as suggesting that: i) the seismogenic ed as a pulse in the earthquake hypocenter, Nevertheless, bearing in mind the relatively regions at the boundary of tectonic plates radi- higher frequency components cannot propa- few statistical analyses which have been done, ate ULF EM emissions observed by satellites in gate over long distances in the lithosphere due the corresponding results still seem to be the topside ionosphere; and ii) that this EM to severe attenuation. Only ultralow and ambiguous. Only a part of them have shown a radiation is not only related with the occur- extremely low frequency (ULF/ELF) waves can temporal and spatial correlation between the rence time of great (M≥5) earthquakes, but it reach the Earth’s surface Hayakawa.14 Freund15 EM waves and the seismic events.2,19,20 So, the is often present in intermediate times and it suggests that during the build-up of stress question whether there is a relationship appears as a quasi-permanent phenomenon. before EQs, charge carriers are able to flow out between the seismic activity of an area and the of the stressed rock volume into surrounding EM radiation in the space over this specific rocks. Such outflow constitutes an electric cur- area is still open.21 In this study we are further [Research in Geophysics 2014; 4:5001] [page 31] Article elaborating the above question. by ICE/DEMETER between 20:25:00 - 20:27:00 we examine the northwest part of the Greek Specifically, instead of studying the ULF EM UT/37°-39° lat. The results of our filtering Arc, a rectangular region with latitudes wave activity around the time of an earthquake method applied to this signal is shown in between N 36°-39° and longitudes E 19°-22° occurrence near its epicentre, we compare the Figure 1C; the energy fluctuation shown in (seismic region marked as R1). As we can see ULF EM wave energy in the topside ionosphere Figure 1D was found to reach a value as high in Figure 2A, the region R1 (marked by the red with the seismic activity of various geographic as 0.21 (mV/m)2. border line) shows stronger seismic activity, regions of historically high seismicity, includ- between the years 2000 and 2008, than its ing boundaries of tectonic plates. Our study eastern neighbouring region R2 (marked by focuses on certain regions such as the Eastern green border line). Given that both of the areas Mediterranean Sea, Central America, Results (R1 and R2) have the same latitude, they Indonesia and Greece. The results decisively absorb comparable solar energy and have support a spatial correlation between strong The case of seismicity in Greece equivalent geomagnetic conditions. [≥0.02 (mV/m)2] ULF EM radiation and the During a period of four years (2006-2009) a seismogenic regions examined around the Western-Eastern Greece sample of 41 ULF events with energy E≥0.02 boundaries of tectonic plates. The outstanding seismicity of Greece (the (mV/m)2 were recorded above both regions R1 country is ranked third worldwide and first and R2, which are shown by solid circles in among the countries of the European conti- Figure 2B. The size of the circles shown in the nent) is due to its special geological features, figure compared with the numerical scale of Materials and Methods which are shaped by the movements of the the label inserted at the bottom of the figure Eurasian, African and Anatolian tectonic plates indicates the amount of energy of the corre- The satellite DEMETER (Detection of in the Eastern Mediterranean basin. This sponding ULF electromagnetic radiation. Electro-Magnetic Emissions Transmitted from region of high seismicity is known as the From the sample of 41 ULF events, a number Earthquake Regions) was launched on June Greek Arc and is shown in Figure 2A (the seis- of 28 events were recorded above region R1 of 29th, 2004. Its orbit altitude is 710 km, and it mic map has been constructed by the historically high seismicity, whereas only 13 takes 14 orbits per day around the Earth. University of Athens for earthquakes with events were detected above the adjacent Among the scientific objectives of the DEME- magnitude M≥4 in the years 2000-2008).
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