T. Lien, E. Chang, C. Hwang, Ching‐Chung Cheng, Kin-Fai Lam, Rou-Fei Chen, C. Mu
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Delineating a Volcanic Aquifer Using Groundwater-induced Gravity Changes in the Tatun Volcano Group, Taiwan
The Tatun Volcanic Group (TVG) is an active volcano that could cause volcanic hazards in northern Taiwan. The latest phreatic eruption of the TVG occurred some 6000 years ago. Understanding the state of groundwater around the TVG can be a crucial step towards effectively assessing the risk of phreatic explosion by providing information about the sources of groundwater and the media it flows. We measured gravity changes at a superconducting gravity station and several groundwater-sensitive sites to examine the way the groundwater altered the gravity values around the TVG. Groundwater-induced gravity changes are simulated by two hydrological models (A and B). Both models show coherent seasonal variations in groundwater level and gravity value in the center of the TVG (Chintiengang). This coherence indicates inter-connected porous media for free groundwater flows below Chintiengang. However, inconsistencies between the modeled and observed gravity changes occurred in the eastern part of the TVG, suggesting here highly heterogeneous formations with fractures and barriers may exist below Chihsinshan and Dayoukeng. The gravity consistencies and inconsistencies between the observations and the models are used to delineate a volcanic aquifer, which can provide additional information for assessing the probability of a potential phreatic eruption over the TVG.
期刊介绍:
The major publication of the Chinese Geoscience Union (located in Taipei) since 1990, the journal of Terrestrial, Atmospheric and Oceanic Sciences (TAO) publishes bi-monthly scientific research articles, notes, correspondences and reviews in all disciplines of the Earth sciences. It is the amalgamation of the following journals:
Papers in Meteorological Research (published by the Meteorological Society of the ROC) since Vol. 12, No. 2
Bulletin of Geophysics (published by the Institute of Geophysics, National Central University) since No. 27
Acta Oceanographica Taiwanica (published by the Institute of Oceanography, National Taiwan University) since Vol. 42.