Schumann Resonance anomalies possibly associated with large earthquakes in Mexico
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ORIGINAL PAPER
Schumann Resonance anomalies possibly associated with large earthquakes in Mexico P Sierra Figueredo1*
, B Mendoza Ortega2, M Pazos3, D Rodrı´guez Osorio4, E Andrade Mascote4, V M Mendoza3 and R Gardun˜o3 1
Instituto de Geofı´sica y Astronomı´a, CITMA, C.P. 11600 La Lisa, Havana, Cuba
2
Escuela Nacional de Ciencias de la Tierra, Universidad Nacional Auto´noma de Me´xico, C.P. 04510 Mexico City, Mexico 3
Centro de Ciencias de la Atmo´sfera, Universidad Nacional Auto´noma de Me´xico, C.P. 04510 Mexico City, Mexico 4
Instituto de Geofı´sica, Universidad Nacional Auto´noma de Me´xico, C.P. 04510 Mexico City, Mexico Received: 11 December 2019 / Accepted: 04 May 2020
Abstract: Using Schumann Resonance (SR) data of a station located in Mexico, we analyzed anomalies in frequency and amplitude of the first three SR harmonics within a window of 21 days, 15 days before and 5 days after, of 12 earthquakes of magnitude M [ 5 that occurred in the Mexican Pacific coast. The period of study was from June 2013 to May 2018. In order to avoid SR anomalies likely produced by solar activity, we discarded periods with solar proton events; also, we distinguished three levels of geomagnetic activity (low, medium and high). We found either positive or negative statistically significant anomalies in frequency and amplitude around the day of the seismic event. However, a study of anomalies in periods of earthquakes of magnitude lower than M [ 5 and quiet solar activity conditions also shows statistically significant anomalies. Therefore, these results concerning the presence of SR anomalies around the time of earthquakes in Mexico using the Mexican SR station data are not conclusive. Keywords: Schumann Resonance; Mexican earthquakes; Seismic events; ELF signals
1. Introduction The Schumann Resonance (SR) consists of the electromagnetic resonances generated inside the capacitor formed by the terrestrial surface and the low ionosphere. These signals appear in the extremely low frequency (ELF) band between 5 and 50 Hz. They are caused by the global electric activity, and its variations are produced by the solar and geophysical activities [1]. Large seismic events, besides the scientific challenges they pose, have huge social and economic impacts; then, it is necessary to study them from all possible points of view. Several papers have addressed the problem of SR anomalies associated with large earthquakes [2–7]. In this context, the radius of the vertical atmospheric perturbation is close to the seismic focus [8]. Up to now, the proposed mechanisms of such association are: surface
electromagnetic radiation associated with fast charge and electromagnetic field fluctuations due to an ensemble of opening microfractures (cracks) in the ultra-low frequency (ULF) band (0.01–10 Hz) observed before and after earthquakes [8] or gases leaking from the crust over the active tectonic faults that serve as carrier for radon, in the atmosphere they form large ion clusters that change the conductivity and parameters of the global elect
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