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| Titel |
Detection of ULF geomagnetic signals associated with seismic events in Central Mexico using Discrete Wavelet Transform |
| VerfasserIn |
O. Chavez, J. R. Millan-Almaraz, R. Perez-Enriquez, J. A. Arzate-Flores, A. Kotsarenko, J. A. Cruz-Abeyro, E. Rojas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 10, no. 12 ; Nr. 10, no. 12 (2010-12-14), S.2557-2564 |
| Datensatznummer |
250008535
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| Publikation (Nr.) |
 copernicus.org/nhess-10-2557-2010.pdf |
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| Zusammenfassung |
| The geomagnetic observatory of Juriquilla Mexico, located at
longitude –100.45° and latitude 20.70°, and 1946 m a.s.l.,
has been operational since June 2004 compiling geomagnetic field measurements
with a three component fluxgate magnetometer. In this paper, the results of
the analysis of these measurements in relation to important seismic activity
in the period of 2007 to 2009 are presented. For this purpose, we used
superposed epochs of Discrete Wavelet Transform of filtered signals for the
three components of the geomagnetic field during relative seismic calm, and
it was compared with seismic events of magnitudes greater than Ms > 5.5,
which have occurred in Mexico. The analysed epochs consisted of 18 h
of observations for a dataset corresponding to 18 different earthquakes
(EQs). The time series were processed for a period of 9 h prior to and 9 h
after each seismic event. This data processing was compared with the same
number of observations during a seismic calm. The proposed methodology proved
to be an efficient tool to detect signals associated with seismic activity,
especially when the seismic events occur in a distance (D) from the
observatory to the EQ, such that the ratio D/ρ < 1.8 where ρ is the
earthquake radius preparation zone. The methodology presented herein shows
important anomalies in the Ultra Low Frequency Range (ULF; 0.005–1 Hz),
primarily for 0.25 to 0.5 Hz. Furthermore, the time variance (σ2)
increases prior to, during and after the seismic event in relation to the
coefficient D1 obtained, principally in the Bx (N-S) and By (E-W) geomagnetic
components. Therefore, this paper proposes and develops a new methodology to
extract the abnormal signals of the geomagnetic anomalies related to
different stages of the EQs. |
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