Volume 6 • Issue 1 • 1000250 J Earth Sci Clim Change ISSN:2157-7617 JESCC, an open access journal Research Article Open Access Petraki et al., J Earth Sci Clim Change 2015, 6:1 http://dx.doi.org/10.4172/2157-7617.1000250 Review Article Open Access Earth Science & Climatic Change *Corresponding author: Nikolopoulos D, TEI of Piraeus, Department of Electronic Computer Systems Engineering, Petrou Ralli and Thivon 250, GR- 12244 Aigaleo, Athens, Greece, Tel: +0030-210-5381560; Fax: +0030-210- 5381436; E-mail: dniko@teipir.gr Received November 16, 2014; Accepted January 03, 2015; Published January 12, 2015 Citation: Petraki E, Nikolopoulos D, Nomicos C, Stonham J, Cantzos D, et al. (2015) Electromagnetic Pre-earthquake Precursors: Mechanisms, Data and Models-A Review. J Earth Sci Clim Change 6: 250. doi:10.4172/2157-7617.1000250 Copyright: © 2015 Petraki E, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Electromagnetic Pre-earthquake Precursors: Mechanisms, Data and Models-A Review Petraki E 1 , Nikolopoulos D 2 *, Nomicos C 3 , Stonham J 1 , Cantzos D 4 , Yannakopoulos P 2 and Kottou S 5 1 Brunel University, Department of Engineering and Design, Kingston Lane, Uxbridge, Middlesex UB8 3PH, London, UK 2 TEI of Piraeus, Department of Electronic Computer Systems Engineering, Petrou Ralli and Thivon 250, GR-12244 Aigaleo, Athens, Greece 3 TEI of Athens, Department of Electronic Engineering, Agiou Spyridonos, GR-12243, Aigaleo, Athens, Greece 4 TEI of Piraeus, Department of Automation Engineering, Petrou Ralli and Thivon 250, GR-12244 Aigaleo, Greece 5 University of Athens, Medical School, Department of Medical Physics, Mikras Asias 75, GR-11527 Goudi, Athens, Greece Keywords: Electromagnetic emissions; Earthquake precursors; Ultra low frequency Introduction Natural events like earthquakes, tsunamis and volcanic eruptions are inevitable. What makes these events more dangerous and disastrous is not that they are inevitable but that they are still extremely hard to predict. herefore, it is one of the major challenges for the world scientiic community to ind a reliable seismic precursor. he researchers have started eforts in this direction a lot of decades ago. However, the problem of earthquake prediction remains unsolved. Precursors recorded for certain earthquakes indicate there is evidence that they can be used for forecasting. In case of an earthquake rupture, certain precursory activity can be expected, if the observation is made in the near vicinity of causative fracture. he problem of earthquake prediction consists of consecutive, step-by-step, narrowing of the time interval, space and magnitude ranges, where a strong earthquake should be expected [1]. Five stages of prediction are usually distinguished. he background stage provides maps with the territorial distribution of the maximum possible magnitude and recurrence time of destructive earthquake of diferent magnitudes. Four subsequent stages, fuzzily divided, include the time prediction; they difer in the characteristic time interval covered by an alarm. hese stages are as follows [2]: long- term (10 1 years); intermediate-term (1 year); short-term (10 -1 to 10 -2 years), and immediate-term (10 -3 years or less). Such division into stages is dictated by the character of the process that leads to a strong earthquake and by the needs of earthquake preparedness; the latter comprises an arsenal of safety measures for each stage of prediction [1]. According to Hayakawa and Hobara [3] the prediction of earthquakes is classiied into three categories: long-term (timescale of 10 to 100 years); intermediate-term (time-scale of 1 to 10 years); short-term. Note, that even in short-term prediction there is no one-to-one correspondence between anomalies in the observations and the earthquake events [4,5]. Although much more diicult than the long-term and intermediate- term predictions, short-term prediction of earthquakes on a time-scale of hours, days or weeks, is believed to be of the highest priority for social demands in seismo-active countries. he short-term earthquake precursors related with electromagnetic efects are promising tools for earthquake prediction. he subjective study of seismo-electromagnetism refers to electric and magnetic ield anomalies [6] observed during seismicity. Various studies have shown that these pre-seismic electromagnetic emissions occur in wide frequency band ranging from few Hz to MHz. Global eforts to predict earthquakes were started about a century ago and peaked during 1970s. he irst scientiically well documented earthquake prediction was made on the basis of temporal and spatial variation of ts/tp relation in Blue mountain Lake, New York on 3rd August, 1973 [7]. Seismologists then successfully predicted the M7.4 Heicheng China earthquake of February 4, 1975 (Cha Chi Yuan), which raised the hopes that it could be possible to make reliable earthquake forecasts. Because of this prediction, an alert was issued within the 24-hour period prior to the main shock, probably preventing a larger number of casualties than the 1328 deaths that actually occurred from this event. However, the failure to predict another devastating earthquake 18 months later, the 1976 M7.8 Tangshan earthquake, was a major setback to the earthquake prediction efort. Casualties from this earthquake numbered in the hundreds of thousands [8]. he seismologists have now narrowed down their studies from long term prediction to short term prediction [9]. he studies carried out in past three decades have given birth to the new ield of seismo-electromagnetism. Several research groups all over the world have shown evidences of electromagnetic emissions and anomalies before earthquakes. Despite the scientiic eforts, the preparation and evolution of earthquakes is not delineated yet. A signiicant reason is that there is restricted knowledge of the fracture mechanisms of the crust [4,10-26]. his is reinforced by the fact that each earthquake is particular and Abstract This paper is a survey of pre-earthquake short-term electromagnetic precursors. Extensive studies were carried out the last decades in analysis of electromagnetic emissions from 10-3 Hz up to MHz. These signals were analyzed through visual, statistical and chaotic techniques. The paper presents cumulative elements from scientiic investigations performed during the last 40 years in this area. Physical models have also been developed for the interpretation of production and propagation of electromagnetic radiation during the fracture process. The Ultra Low Frequency (ULF) fracture-re-lated emissions attempted to be explained via magneto-hydrodynamic, piezomagnetic and electroki-netic effects whereas for the kHz-MHz observations the model of asperities was proposed.