Anomalous frequency characteristics of groundwater level before major earthquakes in Taiwan

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題名:	Anomalous frequency characteristics of groundwater level before major earthquakes in Taiwan
作者:	顏宏元;Chen, C.-H.;Wang, C.-H.;Wen, S.;Yeh, T.-K.;Lin, C.-H.;Liu, J.-Y.;Yen, H.-Y.;Lin, C.;Rau, R.-J.;Lin, T.-W.
貢獻者:	地球科學學院地球科學學系
關鍵詞:	Alluvial fans;Amplitudes;Earthquake intensity;Earthquakes;Frequency bands;Groundwater;Groundwater levels;Mathematical analysis;Precipitation;Seismic activity;Seismic phenomena;Seismology;Water wells;Wells
日期:	2013-06-24
上傳時間:	2026-04-23 11:29:26 (UTC+8)
出版者:	European Geosciences Union;Katlenburg-Lindau: Copernicus Publications
摘要:	摘要： 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. 出版者： Katlenburg-Lindau: Copernicus Publications 出版日期： 2013-05-02 出處： Hydrology and Earth System Sciences, 2013-05, Vol.17 (5), p.1693-1703 資源來源： Agricultural & Environmental Science Collection 版權： COPYRIGHT 2013 Copernicus GmbH 版權： Copyright Copernicus GmbH 2013 識別號： ISSN: 1607-7938 識別號： ISSN: 1027-5606 識別號： EISSN: 1607-7938 識別號： DOI: 10.5194/hess-17-1693-2013
顯示於類別:	[地球科學學系] 期刊論文

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