doi: 10.29382/eqs-2018-0005-5 Seismic electric signals in seismic prone areas * Nicholas V. Sarlis 1,2 , * Panayiotis A. Varotsos 1,2 Efthimios S. Skordas 1,2 Seiya Uyeda 3 Jacques Zlotnicki 4 Toshiyasu Nagao 5 Anatoly Rybin 6 Mary S. Lazaridou-Varotsos 2 Konstantina A. Papadopoulou 1 1 Section of Solid State Physics, Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos 157 84, Athens,Greece 2 Solid Earth Physics Institute, Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos 157 84, Athens, Greece 3 Section II, Division 4, Japan Academy, Tokyo, 110-0007, Japan 4 EMSEV (http://www.emsev-iugg.org/emsev/) and CNRSDR7, Observatoire de Physique du Globe de Clermont-Ferrand, Laboratoire Magmas et Volcans, 5 rue Kessler 63000 Clermont Ferrand, France 5 EMSEV (http://www.emsev-iugg.org/emsev/) and Institute of Oceanic Research and Development, Tokai University, Shizuoka 424-0902, Japan 6 Research Station RAS, Bishkek-49, Kyrgyzstan Abstract The Varotsos-Alexopoulos-Nomicos (VAN) method of short-term earthquake prediction was introduced in the 1980s. The VAN method enables estimation of the epicenter, magnitude and occurrence time of an impending earthquake by observing transient changes of the electric field of the Earth termed seismic electric signals (SES). Here, we present a few examples of SES observed in various earthquake prone areas worldwide. Keywords: seismic electric signals; VAN method; earthquake prediction; EMSEV-Bishkek RS-RAS cooperation 1 Introduction Varotsos-Alexopoulos-Nomicos (VAN) method indi- cates major earthquakes (EQs) are preceded by transient changes of the Earth’s electric field termed seismic electric signals (SES) (Varotsos and Alexopoulos, 1984a, b). The motivation of the present paper is as follows: In general, a short term earthquake prediction method is of course more useful if it can be applied to seismic prone areas of different geological and tectonic environment. Thus, here we recapitulate various seismic areas at which SES experimentation has long been performed and include also those areas at which relevant experiments have recently started. In Section 2, discrimination of SES from noise and the properties of SES useful for EQ prediction are summarized. In Sections 3, 4, 5, and 6, we focus on SES that have been recorded in Greece, SES and SES-like signals observed in Japan, China and Mexico, respectively. Finally in Section 7, we present possible SES recorded in Kyrgyzstan during the recent collaboration between the IAGA-IASPEI-IAVCEI Inter Association Working Group on Electromagnetic Studies of Earthquakes and Volcanoes (EMSEV http://www.emsev-iugg.org/emsev/) and the Bishkek Research Station of the Russian Academy of Sciences (RS-RAS http://www.gdirc.ru/en/) in Kyrgyzstan. 2 Background on seismic electric signals 2.1 Distinction of SES from noise The simultaneous use of several long and short measuring dipoles with different directions and lengths was found necessary and effective for distinction of SES from noise. The fact that SES are emitted in the preparation volume of the future EQ usually at a distance of the order of 100 km away from the field station is exploited against to other sources such as magneto-telluric (MT), lightning or man-made artificial noises. Varotsos and Lazaridou (1991) showed that for SES the values of ratio ΔV/L for parallel measuring dipoles (ΔV is potential difference and L is length) are approximately the same. In * Received 31 January 2017; accepted in revised form 28 January 2018; published 15 April 2018. * Corresponding author. e-mail: nsarlis@phys.uoa.gr © The Seismological Society of China and Institute of Geophysics, China Earthquake Administration 2018 Earthq Sci (2018)31: 44–51 44