Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 5.153
IF5.153
IF 5-year value: 5.460
IF 5-year
5.460
CiteScore value: 7.8
CiteScore
7.8
SNIP value: 1.623
SNIP1.623
IPP value: 4.91
IPP4.91
SJR value: 2.092
SJR2.092
Scimago H <br class='widget-line-break'>index value: 123
Scimago H
index
123
h5-index value: 65
h5-index65
Volume 17, issue 5
Hydrol. Earth Syst. Sci., 17, 1693–1703, 2013
https://doi.org/10.5194/hess-17-1693-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Hydrol. Earth Syst. Sci., 17, 1693–1703, 2013
https://doi.org/10.5194/hess-17-1693-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 May 2013

Research article | 02 May 2013

Anomalous frequency characteristics of groundwater level before major earthquakes in Taiwan

C.-H. Chen1, C.-H. Wang1, S. Wen2, T.-K. Yeh3, C.-H. Lin1, J.-Y. Liu4,5, H.-Y. Yen6, C. Lin7, R.-J. Rau7, and T.-W. Lin8 C.-H. Chen et al.
  • 1Institute of Earth Sciences, Academia Sinica, Taipei 115, Taiwan
  • 2National Center for Research on Earthquake Engineering, Taipei 106, Taiwan
  • 3Department of Real Estate and Built Environment, National Taipei University, New Taipei City 237, Taiwan
  • 4Institute of Space Science, National Central University, Jhongli 320, Taiwan
  • 5Center for Space and Remote Sensing Research, National Central University, Jhongli 320, Taiwan
  • 6Institute of Geophysics, National Central University, Jhongli 320, Taiwan
  • 7Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan
  • 8Seismological Center, Central Weather Bureau, Taipei 100, Taiwan

Abstract. 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.

Publications Copernicus
Download
Citation