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| Titel |
Ultra low frequency (ULF) electromagnetic anomalies associated with large earthquakes in Java Island, Indonesia by using wavelet transform and detrended fluctuation analysis |
| VerfasserIn |
F. Febriani, P. Han, C. Yoshino, K. Hattori, B. Nurdiyanto, N. Effendi, I. Maulana, E. Gaffar |
| 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 Sciences ; 14, no. 4 ; Nr. 14, no. 4 (2014-04-10), S.789-798 |
| Datensatznummer |
250118386
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| Publikation (Nr.) |
 copernicus.org/nhess-14-789-2014.pdf |
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| Zusammenfassung |
| Indonesia is one of the most seismically active regions
in the world and mitigation of seismic hazard is important. It is reported
that Ultra low frequency (ULF) geomagnetic anomalies are one of the most convincing phenomena
preceding large earthquakes (EQs). In this paper we have analyzed geomagnetic data at
Pelabuhan Ratu (PLR) (7.01° S, 106.56° E), Sukabumi, West
Java, Indonesia, from 1 September 2008 to 31 October 2010.
There are twelve moderate–large EQs (M ≥ 5) within 160 km from the
station during the analyzed period. The largest one is the M =7.5 EQ
(depth = 57 km, epicentral distance = 135 km, 2 September 2009) based on EQ
catalog of Indonesian Meteorological, Climatological and Geophysical Agency
(BMKG). To investigate the ULF geomagnetic anomalous variations preceding
all the EQs, spectral density ratio at the frequency range of 0.01 ± 0.003 Hz based on wavelet transform (WT) and detrended fluctuation
analysis (DFA) have been carried out. The spectral density ratio results
show the enhancements a few weeks before the largest EQ. The enhancement
persists about one week and reaches a maximum on 16 August 2009. At the
same time, the result of the DFA presents the decrease of α value.
For other EQs, there are no clear increases of the spectral density ratio
with simultaneous decrease of α value. When these phenomena occur,
the value of Dst index shows that there are no peculiar global geomagnetic
activities at the low latitude region. The above results are suggestive of
the relation between the detected anomalies and the largest EQ. |
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