Articles | Volume 5, issue 5
Nat. Hazards Earth Syst. Sci., 5, 711–715, 2005

Special issue: Seismic hazard evaluation, precursory phenomena and seismo...

Nat. Hazards Earth Syst. Sci., 5, 711–715, 2005

  22 Sep 2005

22 Sep 2005

Possible seismogenic origin of changes in the ULF EM resonant structure observed at Teoloyucan geomagnetic station, Mexico, 1999-2001

A. Kotsarenko1, O. Molchanov2, R. Pérez Enríquez1, J. A. López Cruz-Abeyro1, S. Koshevaya3, V. Grimalsky4, and I. Kremenetsky5 A. Kotsarenko et al.
  • 1Centro de Geociencias en Juriquilla, UNAM, Apdo Postal 1-742, Centro Queretaro, Querétaro, C.P. 76001, Mexico
  • 2Institute of the Physics of the Earth, Moscow, Russia
  • 3UAEM, Cuernavaca, Morelos, Mexico
  • 4INAOE, Tonantzintla, P.O.51 & 216, C.P. 72000, Puebla, Pue., Mexico
  • 5Institute of Space Research, Nat. Acad. Sci. and Nat. Space Agency, Ukraine

Abstract. The evolution of the ULF resonant structure observed at Teoloyucan geomagnetic station has been provisionally studied in a possible relation with seismic activity in Mexico in the period 1999-2001. Two resonant lines were observed in the H-component (linear polarization) in the frequency bands fR2=10.2–11.1 mHz and fR2=13.6–14.5 mHz, sometimes accompanied by other harmonics. The source of the observed resonances is possibly related with the geomagnetic location of the station (geomagnetic latitude λ=29.1°) and its proximity to the equatorial electrojet (λ~30°). An enhancement of the carrier frequency of both resonances in the period 1 month–2 weeks was found before the strongest EQs. Also, a depression of the resonant structure just a few days before and a few days after some EQs seems to be correlated with seismic activity.