NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-3-203-2003 Preseismic ULF electromagnetic effect from observation at Kamchatka Molchanov O. 1 Schekotov A. 1 Fedorov E. 1 Belyaev G. 1 Gordeev E. 2 Institute of the Physics of the Earth, Moscow, Russia Institute of Geophysical Survey, Petropavlovsk-Kamchatski, Russia 31 08 2003 3 3/4 203 209 Copyright: © 2003 O. Molchanov et al. 2003 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://nhess.copernicus.org/articles/3/203/2003/nhess-3-203-2003.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/3/203/2003/nhess-3-203-2003.pdf

Some results of ULF magnetic field observation at Karimshino site (Kamchatka, Russia) since June 2000 to September 2001 are presented here. Using case study we have found an effect of suppression of ULF intensity about 2–6 days before rather strong and nearby seismic shocks (magnitude <i>M</i> = 4.0 – 6.2). It is revealed for nighttime and horizontal component of ULF field (<i>G</i>) in the frequency range 0.01 – 0.1 Hz. Then we prove the reliability of the effect by computed correlation between <i>G</i> (or 1/<i>G</i>) and specially calculated seismic indexes K<sub>s</sub> for the whole period of observation. Basing on the simple criteria we conclude that reliability of seismo-associated ULF suppression effect is comparable with well-known effect of connection between ULF variation and K<sub>p</sub> index of global magnetic activity. It seems the reason of suppression is located at the atmosphere or ionosphere but not in the ground medium.