Analysis of Abnormal Streamflow Changes due to the Chi-Chi Earthquake
Date Issued
2008
Date
2008
Author(s)
Chung, Po-Yu
Abstract
An ML 7.3 earthquake occurred near the town of Chichi in central Taiwan at 01:47 September 21, 1999. Among 411 monitoring wells, 291 wells located at 138 hydrogeological stations recorded coseismic changes in groundwater level during the Chi-Chi earthquake. The coseismic changes ranged from a rise of 7.42 m to a fall of 11.09 m. Coseismic groundwater level changes may reflect the redistribution of tectonic stress and crustal strain, which may induce abnormal changes in streamflow. Changes of river discharge induced by the Chi-Chi earthquake were recorded at 34 out of 124 stream gauges in Taiwan. These 34 gauges located approximately between 5 to 145 km from the epicenter, where 32 gauges recorded surging flow and 2 gauges, Tong-Tou and Shui-Li bridge, recorded a decrease of discharge. The finite element method was adopted to analyze three different types of aquifer, including unconfined aquifer, semi-confined aquifer and confined aquifer. The purposes are to understand the process of how the lateral compression induces excess pore pressure restoration and to realize how the mechanism affect the abnormal streamflow changes. In this study, we are going to focus on two targets. One is the abnormal streamflow changes and the other is the mechanism of these changes induces by earthquakes.
Subjects
Chi-Chi
abnormal streamflow
groundwater
discharge
earthquake
coseismic
Type
thesis
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