Study of ultra low frequency signals (0.01–10 Hz) associated with moderate earthquake occurred in Koyna region using induction type magnetic sensor

Study of magnetic field fluctuations due to earthquakes have been started at Shivaji University, Kolhapur (India) using three axis ULF/VLF induction type magnetic sensors, since March 2006. We have considered one event of moderate earthquake (4.0<;M<;5.0) for the present study. This earthquake occurred in Koyna region on 14^th November 2009 at 13:03:35 UT (M=4.8). For study of these signals we have taken the frequency band ranging from 0.01 Hz to 10 Hz which is one of the most promising candidates for short term earthquake prediction. Suitable Data analysis methods like power spectral density, fractal analysis etc. are used. This analysis gives the detail information about the possibilities of precursory signals due to moderate seismic activities near the observation site. A variation in the polarization parameter during seismic events is discussed in the present investigation in the light of geomagnetic activities.