Possible seismogenic origin of changes in the ULF EM resonant structure observed at Teoloyucan geomagnetic station, Mexico, 1999-2001
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 <i...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2005-01-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | http://www.nat-hazards-earth-syst-sci.net/5/711/2005/nhess-5-711-2005.pdf |
| Summary: | 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 <i>f<sub>R2</sub></i>=10.2–11.1 mHz and <i>f<sub>R2</sub></i>=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. |
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| ISSN: | 1561-8633 1684-9981 |