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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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We developed a methodology that generate free-externally disturbed magnetic variations in ground magnetometers close to the Chilean convergent margin. Spectral analysis (~ mHZ) and magnetic anomalies increased prior large Chilean earthquakes (Maule 2010 Mw8.8, Iquique 2014 Mw8.2 and Illapel 2015 Mw8.3). These findings are related to micro cracks within lithosphere due changes in the stress states. These physical evidence should be thought as a last stage of earthquake preparation process.
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https://doi.org/10.5194/nhess-2020-354
https://doi.org/10.5194/nhess-2020-354

  26 Nov 2020

26 Nov 2020

Review status: this preprint is currently under review for the journal NHESS.

Long-term magnetic anomalies and its possible relationship to the latest Greater Chilean earthquakes in the context of the seismo-electromagnetic theory

Enrique Guillermo Cordaro1,2, Patricio Venegas-Aravena1,3, and David Laroze4 Enrique Guillermo Cordaro et al.
  • 1Observatorios de Radiación Cósmica y Geomagnetismo, Dep. Física, F. C. F. M. Universidad de Chile, Casilla 487-3, Santiago, Chile
  • 2Facultad de Ingeniería, Universidad Autónoma de Chile, Pedro de Valdivia 425, Santiago, Chile
  • 3Department of Structural and Geotechnical Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Macul, Santiago, Chile
  • 4Instituto de Alta Investigación, CEDENNA, Universidad de Tarapacá, Casilla 7D, Arica, Chile

Abstract. Several magnetic measurements and theoretical development from different research groups have shown certain relationship with worldwide geological processes. Secular variation of geomagnetic cut off rigidity, magnetic frequencies, or magnetic anomalies have been linked with spatial properties of active convergent tectonic margin or earthquakes occurrences during recent years. These include the rise of similar fundamental frequencies in the range of micro hertz before Maule 2010, Japan 2011, and Sumatra 2004 earthquakes and the dramatic rise of the cumulative number of magnetic anomalous peaks before several earthquakes as Nepal 2015 and Mexico 2017, among others. Currently, all of these measurements have been physically explained by the microcrack generation due uniaxial stress change in rock experiments. The basic physics of these experiments have been used to describe the lithospheric behavior in the context of the seismo-electromagnetic theory. Due to the dramatic increase in experimental evidence, physical mechanism and theoretical framework, this paper analyses vertical magnetic behavior close to the latest three main earthquakes in Chile: Maule 2010 (Mw8.8), Iquique 2014 (Mw8.2), and Illapel 2015 (Mw8.3). The FFT, Wavelet transform and daily cumulative number of anomalies methods were used during quiet space weather time during one year before and after each earthquake in order to filter space influence. FFT Method confirm the raise of power spectral density in mHz range before one month each earthquake, which decrease to lower values after some months after earthquake occurrence. The cumulative anomalies method exhibited and increase previous to each Chilean earthquake (50–90 days prior earthquakes) similar to those found for Nepal 2015 and Mexico 2017. The wavelet analyses also show as similar properties as FFT analysis. However, the lack of physics-based constrain in the wavelet analysis do not allow conclusion as strong as FFT and cumulative methods. By using these results and previous research, it could be stated that these magnetic features could give seismic information from impending events. Additionally, these results could be related to the Lithosphere–Atmosphere–Ionosphere coupling (LAIC effect) and the growth of micro cracks and electrification in rocks described by the seismo-electromagnetic theory.

Enrique Guillermo Cordaro et al.

 
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Enrique Guillermo Cordaro et al.

Enrique Guillermo Cordaro et al.

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Short summary
We developed a methodology that generate free-externally disturbed magnetic variations in ground magnetometers close to the Chilean convergent margin. Spectral analysis (~ mHZ) and magnetic anomalies increased prior large Chilean earthquakes (Maule 2010 Mw8.8, Iquique 2014 Mw8.2 and Illapel 2015 Mw8.3). These findings are related to micro cracks within lithosphere due changes in the stress states. These physical evidence should be thought as a last stage of earthquake preparation process.
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