Journal cover Journal topic
Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
Ann. Geophys., 36, 275-285, 2018
https://doi.org/10.5194/angeo-36-275-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Regular paper
01 Mar 2018
Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin
Enrique G. Cordaro1,2, Patricio Venegas1,3, and David Laroze4,5 1Observatorios de Radiación Cósmica, Universidad de Chile, Casilla 487-3, Santiago, Chile
2Facultad de Ingeniería, Universidad Autónoma de Chile, Pedro de Valdivia 425, Santiago, Chile
3Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile
4Instituto de Alta Investigación, CEDENNA, Universidad de Tarapacá, Casilla 7D, Arica, Chile
5School of Physical Sciences and Nanotechnology, Yachay Tech University, 00119 Urcuquí, Ecuador
Abstract. We present a different view of secular variation of the Earth's magnetic field, through the variations in the threshold rigidity known as the variation rate of geomagnetic cutoff rigidity (VRc). As the geomagnetic cutoff rigidity (Rc) lets us differentiate between charged particle trajectories arriving at the Earth and the Earth's magnetic field, we used the VRc to look for internal variations in the latter, close to the 70° south meridian. Due to the fact that the empirical data of total magnetic field BF and vertical magnetic field Bz obtained at Putre (OP) and Los Cerrillos (OLC) stations are consistent with the displacement of the South Atlantic magnetic anomaly (SAMA), we detected that the VRc does not fully correlate to SAMA in central Chile. Besides, the lower section of VRc seems to correlate perfectly with important geological features, like the flat slab in the active Chilean convergent margin. Based on this, we next focused our attention on the empirical variations of the vertical component of the magnetic field Bz, recorded in OP prior to the Maule earthquake in 2010, which occurred in the middle of the Chilean flat slab. We found a jump in Bz values and main frequencies from 3.510 to 5.860 µHz, in the second derivative of Bz, which corresponds to similar magnetic behavior found by other research groups, but at lower frequency ranges. Then, we extended this analysis to other relevant subduction seismic events, like Sumatra in 2004 and Tohoku in 2011, using data from the Guam station. Similar records and the main frequencies before each event were found. Thus, these results seem to show that magnetic anomalies recorded on different timescales, as VRc (decades) and Bz (days), may correlate with some geological events, as the lithosphere–atmosphere–ionosphere coupling (LAIC).
Citation: Cordaro, E. G., Venegas, P., and Laroze, D.: Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin, Ann. Geophys., 36, 275-285, https://doi.org/10.5194/angeo-36-275-2018, 2018.
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Short summary
The interaction between the magnetic field and the particles coming from outer space, which apparently have a relationship with tectonic plates, is studied. The major earthquakes of Maule (2010, 8.8 Mw), Sumatra (2004, 9.2 Mw) and Tohoku (2011, 9.0 Mw) were studied, similar frequencies being found in the vertical component of the magnetic field (microhertz range). The temporal evolution of the magnetic oscillations showed the possible link with the seismic movement of Maule in 2010.
The interaction between the magnetic field and the particles coming from outer space, which...
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