Analysis of the ULF electromagnetic emission related to seismic activity, Teoloyucan geomagnetic station, 1998-2001

Abstract

Abstract.Results of ULF geomagnetic measurements at station Teoloyucan (Central Mexico, 99.11 35.735 W, 19.44 45.100 N, 2280 m height) in relation to seismic activity in the period 1998-2001 and their analysis are presented. Variations of spectral densities for horizontal and vertical components, polarization densities and spectrograms of magnetic field, their derivatives are analyzed as a part of traditional analysis in this study. Values of spectral density were calculated for 6 fixed frequencies f =1, 3, 10, 30, 100 and 300 mHz. Fractal characteristics of spectra were analyzed in the conception of SOC (Self-Organized Criticality). 2 nighttime intervals, 0-3 and 3-6 h by local time have been used to decrease the noise interference in row data. In order to exclude the intervals with a high geomagnetic activity from analysis we referred to Ap indices, calculated for corresponding time intervals. The contribution of seismic events to geomagnetic emission was estimated by seismic index k s =10 0.75Ms /10D, where Ms is the amplitude of the earthquake and D is the distance from its epicenter to the station.

Detection of ULF geomagnetic signals associated with seismic events in Central Mexico using Discrete Wavelet Transform

“…Therefore, a key issue of a study of ULF anomalies is to discriminate signals related to EQs from signals of other origin. Different methods have been proposed to solve this problem, such as the polarization analysis of EM waves (Kawate et al, 1998;Kotsarenko et al, 2004Kotsarenko et al, , 2005Hayakawa et al, 2008); fractal and multi-fractal analysis (Hayakawa et al, 1999;Gotoh et al, 2003;Smirnova et al, 2004;Kotsarenko et al, 2004Kotsarenko et al, , 2005Kotsarenko et al, , 2007; the Principal Component Analysis (PCA) Kotsarenko et al, 2005); location of the area of seismogenic geomagnetic disturbances Kopytenko et al, 2001); and signal/noise discrimination by using the transfer functions , among others. All the abovementioned methods are applied to improve the detection of the ULF signals associated with seismogenic phenomena at different frequencies , and to the understanding of electromagnetic phenomena associated with tectonic and volcanic activity.…”

Detection of electromagnetic anomalies of three earthquakes in Mexico with an improved statistical method

“…Different methods of analysis have been developed: polarization analysis by means of the ratio of vertical magnetic field component to the horizontal (Hayakawa et al, 1996), fractal analysis (mono-and multi-) (Hayakawa et al, 1999;Smirnova et al, 2004;Ida et al, 2005;Ida and Hayakawa, 2006;Kotsarenko et al, 2004Kotsarenko et al, , 2005Kotsarenko et al, , 2007, principal component analysis (Gotoh et al, 2002;Hattori et al, 2004;Kotsarenko et al, 2005), and singular value decomposition , among others.…”

On the modulation of intensity of Alfvén resonances before earthquakes: Observations and model

“…Recently, generation of the seismo-related Ultra Low Frequency (ULF, 0.1-10 Hz) magnetic perturbations, locally generated geomagnetic pulsations, changes in regular resonant structures were confirmed experimentally by different ground-based observations (Kotsarenko et al, 2004(Kotsarenko et al, , 2007. In order to give a possible explanation we link mentioned phenomena with a modification of the parameters of the ionosphere (such as electron density and the temperature), which is regularly detected during satellite observations over earthquake preparation areas (Gousheva et al, 2008;Sarkar et al, 2007).…”