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| Titel |
Anomalous frequency characteristics of groundwater level before major earthquakes in Taiwan |
| VerfasserIn |
C.-H. Chen, C.-H. Wang, S. Wen, T.-K. Yeh, C.-H. Lin, J.-Y. Liu, H.-Y. Yen, C. Lin, R.-J. Rau, T.-W. Lin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 5 ; Nr. 17, no. 5 (2013-05-02), S.1693-1703 |
| Datensatznummer |
250018865
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| Publikation (Nr.) |
 copernicus.org/hess-17-1693-2013.pdf |
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| Zusammenfassung |
| Unusual decreases of water levels were consistently observed in 78%
(= 42/54) of wells in the Choshuichi Alluvial Fan of central Taiwan about 250
days before the Chi-Chi earthquake (M = 7.6 on 20 September 1999) while
possible factors of barometric pressure, earth tides, precipitation as well
as artificial pumping were removed. Variations in groundwater levels measured
on anomalous wells from 1 August 1997 to 19 September 1999, which covers the
250 day unusual decreases, were transferred into the frequency domain to
unveil frequency characteristics associated with the Chi-Chi earthquake.
Analytical results show that amplitudes at the frequency band between
0.02 day−1 and 0.04 day−1 generally maintained at the low stage and
were apparently enhanced a few weeks before the Chi-Chi earthquake.
Variations of amplitude at this particular frequency band were further
examined along with other Taiwan earthquakes (M > 6) from
1 August 1997 to 31 December 2009. Features of the enhanced amplitudes at the
frequency band are consistently observed prior to the other two earthquakes
(the Rei-Li and Ming-Jian earthquakes) during the 12.5 yr study period. In
addition, surface displacements recorded from GPS, which provides insights
into understanding stress status in subsurface during the Chi-Chi earthquake,
are also inspected. The result confirms that abnormal rise and fall changes in
groundwater level yield an agreement with forward and backward surface
displacements around the epicentre prior to the Chi-Chi earthquake. |
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