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| Titel |
Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information |
| VerfasserIn |
G. Prattes, K. Schwingenschuh, H. U. Eichelberger, W. Magnes, M. Boudjada, M. Stachel, M. Vellante, U. Villante, V. Wesztergom, P. Nenovski |
| 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 ; 11, no. 7 ; Nr. 11, no. 7 (2011-07-14), S.1959-1968 |
| Datensatznummer |
250009565
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| Publikation (Nr.) |
 copernicus.org/nhess-11-1959-2011.pdf |
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| Zusammenfassung |
| This work presents ground based Ultra Low Frequency (ULF) magnetic field
measurements in the frequency range from 10–15 mHz from 1 January 2008 to
14 April 2009. In this time period a strong earthquake series hit the
Italian Abruzzo region around L'Aquila with the main stroke of magnitude M = 6.3
on 6 April 2009. In the frame of the South European Geomagnetic Array
(SEGMA), a European collaboration runs ULF fluxgate instruments providing
continuously magnetic field data recorded in mid- and south Europe. The main
scientific objective is the investigation of signal variations due to
seismic activity and the discrimination between other natural and human
influences. The SEGMA station closest to the L'Aquila earthquake epicenter
is L'Aquila observatory located in the epicenter region. For the scientific
analysis we extract the nighttime period from 22:00–02:00 UT and
determine the power spectral density (PSD) of the horizontal (H) and
vertical (Z) magnetic field components and the standardized polarization
ratio (Z) over (H). To discriminate local emissions from global geomagnetic
effects, data from three SEGMA stations in distances up to 630 km from the
epicenter region are analyzed and further compared to the independent global
geomagnetic ∑ Kp index. Apart from indirect ionospheric effects,
electromagnetic noise could be originated in the lithosphere due to tectonic
mechanisms in the earthquake focus. To estimate the amplitude of assumed
lithospheric electromagnetic noise emissions causing anomalies in the PSD of
the (Z) component, we consider magnetotelluric calculations of the electric
crust conductivity in the L'Aquila region. Results found at L'Aquila
observatory are interpreted with respect to the lithosphere electrical
conductivity in the local observatory region, the ∑ Kp index, and
further in a multi station analysis. Possible seismic related ULF anomalies
occur ~2 weeks before the main stroke. |
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